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iHTOOGY 
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/  UNIVERSITY  OF  CALIFORNIA 


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GIFT  OF  THE   PUBLISHER 


No.  Received 


~ 


PRIMARY  LESSONS 


IN 


HUMAN    PHYSIOLOGY 
AND    HEALTH 


BY 


OLIVER    P.    JENKINS,   PH.D. 

PROFESSOR    OF    PHYSIOLOGY   AND    HISTOIOGY    IN    LELAND 
STANFORD    JUNIOR    UNIVERSITY 


NEW   YORK  •:•  CINCINNATI  •:•  CHICAGO 

Q 

AMERICAN    BOOK    COMPANY 


COPYRIGHT,  1906,  BY 
OLIVER  P.   JENKINS. 


606 


A  WORD  TO   THE  TEACHER 

THESE  lessons  have  been  prepared  as  a  guide  to  an 
elementary  study  of  the  body  and  the  essentials  for 
maintaining  its  health.  It  is  assumed  by  the  author 
that  the  book  will  be  used  as  a  guide  only,  and  that  it 
is  the  body  and  its  actions  and  not  the  book  that  is 
to  be  studied.  In  these  years  of  experience  in  teach- 
ing nature  study  and  science  it  has  long  been  con- 
ceded that  the  objects  themselves  present  are  necessary 
for  the  formation  of  clear  conceptions,  and  clear  con- 
ceptions must  be  obtained  or  the  whole  work  will  be  a 
failure.  It  will  be  readily  seen  that  there  are  two 
distinct  subjects  of  these  Lessons,  —  Physiology  and 
Hygiene.  Yet  on  account  of  the  youth  of  the  students 
the  subjects  are  intermingled  in  their  treatment. 

Perhaps  it  would  not  be  out  of  place  at  this  time 
for  the  author  to  state  his  firm  conviction  as  to  the 
relation  of  these  two  subjects. 

The  importance  of  hygiene  will  be  admitted  by  all; 
but  clear  conceptions  of  its  aims  and  teachings  cannot 
exist  without  a  foundation  in  the  knowledge  of  the 
structure  and  functions  of  the  parts  to  be  cared  for. 
This  is  true  for  children  as  well  as  adults.  The  inter- 
est in  pure  air  and  the  desire  to  obtain  it  will  certainly 
be  much  heightened  in  one  who  has  at  least  a  few- 
clear  ideas  of  what  it  is  in  the  air  that  the  body  needs, 
of  where  in  the  body  the  need  exists,  and  what  the 

3 


4  A    WORD   TO    THE   TEACHER 

apparatus  is,  and  how  it  works,  that  brings  the  oxy- 
gen to  the  place  at  which  it  is  needed.  A  knowl- 
edge of  what  the  muscle  is  like,  how  it  is  attached  to  a 
bone,  and  how  it  moves,  adds  greatly  to  the  interest 
in  exercise  of  the  muscle.  So  with  the  heart,  the  eye, 
and  any  other  organ,  —  even  an  elementary  view  of  its 
beautiful  structure  and  the  way  it  performs  its  work 
makes  the  whole  subject  of  its  care  more  interesting 
and  definite. 

One  of  the  causes  of  the  failure  of  physiology  and 
hygiene  to  interest  pupils  is  the  indefiniteness  of  much 
of  the  work  and  the  haziness  of  the  ideas  gained  from 
it.  This,  the  author  believes,  can  be  remedied  by 
making  everything  as  clear  as  possible  by  illustration, 
experiment,  and  observation.  The  subject  then  be- 
comes real  and  the  knowledge  usable,  and  these  quali- 
ties always  insure  a  lively  interest. 

The  recent  growing  interest  in  nature  study  and 
agriculture  as  school  subjects  makes  greater  demands 
on  the  better  teaching  of  physiology  and  hygiene. 
The  structure  of  the  bodies  of  the  domestic  animals 
and  the  functions  of  their  organs  are  in  general  the 
same  as  that  of  the  human  body.  The  laws  of  health 
apply  equally  to  them.  Their  needs  of  exercise, 
good  air,  good  food,  and  sunshine  are  the  same. 
Wounds,  injuries,  and  disease  are  of  the  same  nature 
with  them  as  with  man.  It  is  only  certain  modifica- 
tions of  the  general  knowledge  and  rules  that  are 
necessary  in  each  case.  Physiology,  then,  even  the 
most  elementary,  has  the  responsibility  of  being  an 
introduction  to  a  very  large  field  and  consequently 
requires  all  the  care  and  skill  that  can  be  given  to  it. 


A    WORD   TO   THE   TEACHER  5 

A  word  about  the  anatomical  and  other  terms 
used  in  this  little  book.  The  author  agrees  with  those 
who  oppose  the  introduction  of  terms  which  can 
have  no  meaning  to  the  pupils  after  fair  attention  is 
given  to  the  subject.  But  it  is  certainly  a  mistake 
to  avoid  the  use  of  words  which  are  very  convenient 
terms  for  things  that  have  been  actually  seen.  It 
is  also  a  mistake  to  substitute  terms  not  in  common 
use  for  those  that  are  the  real  names  of  the  parts,  on 
a  supposition  that  it  is  easier  for  the  children.  The 
fact  is  that  such  a  custom  makes  the  work  harder  for 
the  pupils.  The  terms  used  in  this  book,  as  the  author 
knows  by  actual  experience  with  children,  are  as  easily 
learned  as  any  terms  when  the  thing  named  is  seen 
and  its  use  is  understood.  They  are  certainly  fewer  in 
number  and  as  much  within  the  powers  of  the  pupils 
as  are  those  in  the  other  subjects  in  the  school,  —  num- 
ber, language,  and  history,  for  example. 

A  word  also  about  how  far  we  can  go  with  young 
children  in  explaining  various  functions  and  pro- 
cesses of  the  body.  This  depends  much  on  the  method 
of  teaching,  and  teachers  would  differ  greatly  in  their 
judgment.  The  author  believes  that  as  far  as  the 
teacher  does  go,  what  he  gives  should  be  definite  and 
mean  something.  To  illustrate,  some  might  main- 
tain that  with  the  heart  it  is  enough  with  young  pupils 
to  say  that  it  is  a  pump  to  move  the  blood  along,  etc. 
Now,  to  most  of  the  pupils  the  word  pump  conveys  no 
definite  notion.  How  it  works  is  wholly  unknown  to 
them.  Then  there  are  many  kinds  of  pumps.  No 
one  of  them  works  like  the  heart.  None  of  them 
have  valves  like  those  of-  the  heart.  To  make  the 


6  A    WORD   TO   THE   TEACHER 

word  pump  clear  a  pump  must  be  seen  and  its  valves 
examined.  Would  it  not  be  easier  and  far  better  in 
every  way  to  examine  a  heart  at  the  outset  and  see 
what  its  valves  are  like  and  how  they  work.  The 
word  heart  gives  a  real  and  usable  conception,  while 
the  word  pump  without  illustration  and  comparison 
would  be  meaningless.  Heart  is  as  easy  as  pump. 
Illustrations  of  such  indefinite  work  in  physiology 
could  easily  be  multiplied. 

All  of  the  anatomical  and  physiological  parts  of  this 
book  can  be  illustrated  by  parts  of  the  bodies  of  small 
animals.  If  the  part  is  prepared  neatly,  there  can 
be  no  objectionable  feature  about  it.  The  leg  of  a 
chicken  or  of  a  frog  answers  well  to  show  how  muscles 
look  and  how  they  are  attached  to  bones,  how  the 
joints  are  formed,  how  the  nerves  appear,  etc.  These 
animals  will  give  much  other  material.  A  skeleton  of 
a  cat  or -a  dog  will  illustrate  well  the  human  skeleton. 
All  these  preparations  can  be  made  by  the  teacher  or 
by  one  of  the  older  pupils.  It  hardly  need  be  said  that 
no  animal  should  be  killed  before  the  school  or  class, 
or  anything  else  done  that  would  offend  common 
sense.  It  has  been  the  observation  of  the  author 
that  a  personal  knowledge  on  the  part  of  pupils  of  the 
beautiful  structure  of  the  bodies  of  animals  has  the 
effect  of  increasing  the  admiration  for  animals  and 
begetting  a  sympathy  for  them  in  their  bodily  pains 
or  troubles. 

The  human  body  and  the  bodies  of  the  lower  animals 
should  be  studied  also  in  action,  each  in  its  own  natural 
surroundings,  as  organisms  adapted  to  these  surround- 
ings. It  is  only  by  constantly  seeing  the  organisms 


A    WORD   TO   THE   TEACHER  7 

in  their  true  relations  to  other  things  that  even  ele- 
mentary conceptions  of  physiological  facts  can  be 
obtained. 

The  teacher  need  not  feel  discouraged  because  he 
is  not  provided  with  charts  or  other  apparatus;  he  can 
make  use  of  the  living  world  around  him  to  illustrate 
the  study  of  the  most  interesting  of  living  organisms. 
The  work  thus  pursued  will  be  of  real  value  beyond 
the  interesting  knowledge  gained,  and  will  bring  the 
reward  of  a  satisfaction  of  having  accomplished  some- 
thing of  worth. 

In  the  second  book  of  this  series  the  writer  has  intro- 
duced directions  for  the  practical  demonstration  of 
many  anatomical  and  physiological  facts,  which  might 
well  be  suggestive  to  the  teacher  of  this  book.  For 
these  directions  and  for  a  fuller  discussion  of  many  of 
the  subjects  treated  here  reference  may  be  made  to  the 
second  book.  There  are  now  published  many  hand- 
books for  the  dissection  of  many  of  the  groups  of  the 
lower  animals,  any  one  of  which  will  be  helpful  in  pre- 
paring illustrations  for  the  study  of  the  human  body. 

But  illustrations  of  the  work,  or  subjects  of  study, 
will  be  numerous  enough  and  more  vital  if  they 
come  from  observation  and  experience  with  the  objects 
of  study. 

O.  P.  JENKINS. 


CONTENTS 

CHAPTER  PAGE 

I.    How  MOTIONS  OF  THE  BODY  ARE  PRODUCED.    CARE 

AND  EXERCISE  OF  THE  MUSCLES  .        .        .        .11 
II.    SKELETON  OF  THE  UPPER  EXTREMITIES       ...      23 

III.  THE    SKELETON.       HYGIENE    OF    THE    BONES    AND 

JOINTS    o .      31 

IV.  PARTS  OF  THE  CIRCULATORY  ORGANS  .        .        .        -      44 
V.    PHYSIOLOGY    OF   THE    CIRCULATORY    ORGANS.      THE 

BLOOD.     HYGIENE  OF  THE  CIRCULATION      .  52 
VI.    How  THE  BODY  WORKS.     ITS  NEED  FOR  FOOD  AND 

OXYGEN 63 

VII.    FOODS 0        ....  70 

VIII.    PARTS  OF  THE   DIGESTIVE   SYSTEM.     CARE  OF  THE 

TEETH 77 

IX.    DIGESTION.    CARE  OF  THE  DIGESTIVE  ORGANS    .        „  86 

X.     RESPIRATION 95 

XI.    PURE  AIR,  BREATHING,  AND  VENTILATION  .        .        .105 

XII.    THE  SKIN  AND  THE  KIDNEYS 117 

XIII.  CARE  OF  THE  SKIN 125 

XIV.  THE  STRUCTURE  OF  THE  NERVOUS  SYSTEM         .        .130 
XV.    How  THE  NERVOUS  SYSTEM  is  USED.    CARE  OF  THE 

NERVOUS  SYSTEM 138 

9 


10  CONTENTS 

CHAPTER  PAGE 

XVI.    SENSATIONS 147 

XVII.    SIGHT  AND  HEARING 153 

XVIII.    CARE  OF  THE  EYE  AND  EAR 161 

XIX.  DISEASE,  ITS  CAUSES  AND  PREVENTION        .        .        .168 

XX.  ALCOHOL,  TEA,  COFFEE,  TOBACCO,  OPIUM  .        .        .181 


PRIMARY    PHYSIOLOGY 


CHAPTER  I 

HOW   MOTIONS    IN    THE    BODY   ARE    PRODUCED.      CARE 
AND  EXERCISE  OF  THE  MUSCLES 

The  Study  of  the  Human  Body. — The  human  body  is 
made  up  of  a  great  number  of  parts,  which  may  be 
called  so  many  pieces  of  machinery.  They  work  to- 
gether so  harmoniously  that  they  all  help  one  another. 
When,  for  example,  a  boy  climbs  a  tree,  almost  every 
part  of  his  body  is  aiding  in  this  action.  Many 
parts  of  his  arms,  his  legs,  the  muscles  and  bones  of 
the  rest  of  the  body,  the  eye,  the  touch  organs,  the 
nerves,  the  lungs,  the  heart,  and  indeed  almost  all  the 
organs  must  act  together  to  get  the  boy's  body  up 
the  tree. 

To  study  how  these  actions  are  performed,  and 
how  such  a  large  number  of  separate  parts  come 
to  be  so  well  controlled  as  to  accomplish  anything 
the  body  can  do,  is  well  worth  the  trouble  it  takes. 
To  understand  more  clearly  the  parts  of  the  wonder- 
ful machine  which  is  our  constant  servant,  and  to 
learn  how  to  keep  it  in  the  best  order,  is  certainly 
very  important  knowledge. 


12     HOW  MOTIONS  IN  THE  BODY  ARE  PRODUCED 

Study  of  the  Hand  and  Arm.  —  One  may  well  begin 
the  study  of  the  human  body  by  observing  the  com- 
mon movements  of  his  own  arm  and  hand.  Let  him 
pick  up  an  object  from  the  table  and  raise  it  toward 
his  mouth,  and  observe  closely  what  takes  place. 
First,  the  arm  is  straightened — that  is,  the  part  below 
the  elbow,  or  the  forearm,  is  carried  away  from  the 
part  above.  The  whole  arm  may  also  be  moved  away 
from  the  body.  The  hand  is  carried  toward  the  object, 
and  just  as  it  reaches  it,  the  fingers  and  thumb  are 
stretched  out.  The  thumb  and  one  or  more  fingers 
close  together  over  the  object  to  hold  it  firmly,  when 
the  forearm  is  carried  toward  the  upper  arm,  and 
the  hand  with  the  object  is  carried  toward  the  mouth. 
This  is  a  very  common  action,  and  is  repeated  here 
to  observe  just  what  happens.  Let  us  look  at  the 
actions  separately,  and  attempt  to  see  how  they  are 
accomplished. 

Let  us  first  examine  the  fingers  and  the  thumb, 
and  their  actions.  It  is  easy  to  determine  that  each 
finger  has  running  through  its  central  portion  a  row 
of  three  hard  pieces,  which  are  known  well  enough 
to  be  bones.  These  bones  form  two  joints  in  a  finger, 
and  the  one  next  to  the  hand  forms  a  joint  with 
another  bone  at  the  knuckle.  These  joints  allow 
the  fingers  to  fold  toward  the  palm  of  the  hand,  and 
to  unfold  again  until  straight,  or  even  curved  slightly 
backward.  It  is  plain  that  if  it  were  not  for  the 
rigid  parts  and  the  joints  the  fingers  could  not  be 
extended  with  much  force. 

Now  let  us  examine  what  is  the  action  by  which 
the  bones  of  the  finger  are  bent  or  straightened.  If, 


WHAT    THE  MUSCLES  ARE  LIKE  13 

while  one  is  moving  the  forefinger  rapidly  by  ex- 
tending and  bending  it,  he  places  the  finger  of  the 
other  hand  on  the  back  of  the  hand  just  back  of  the 
moving  finger,  he  can  detect  a  firm  cord  crossing 
the  knuckle  and  running  toward  the  wrist.  This  be- 
comes rigid  every  time  the  finger  is  extended.  By 
causing  each  of  the  other  fingers  to  move  in  the  same 
manner,  a  similar  cord  for  each  one  can  be  felt  just 
under  the  skin.  These  cords  can  be  traced  even 
past  the  wrist  into  the  forearm,  where  they  are  lost 
to  the  touch. 

The  skin  of  the  palm  is  thicker  than  that  on  the 
back  of  the  hand,  so  it  is  more  difficult  to  detect 
the  cords  running  from  the  palm  side  of  the  fingers 
at  this  place.  But  if  we  examine  the  region  of  the 
palm  side  of  the  forearm  just  above  the  wrist  while 
the  fingers  are  in  motion,  it  is  easy  to  see  that  there 
is  a  number  of  cords  here  which  are  moved  every  time 
the  fingers  are  bent. 

It  is  plain  from  this  that  the  fingers  are  moved 
backward  and  forward  by  these  strings  pulling,  first 
the  one  set,  then  the  other.  What  pulls  on  the  strings? 
If,  while  the  thumb  and  finger  are  closed  and  opened,  as 
before  observed,  the  other  hand  be  made  to  grasp 
around  the  forearm  just  below  the  elbow,  it  will  be 
found  that  this  part  of  the  arm  shows  great  activity 
beneath  the  skin.  This  is  due  to  the  action  of  the 
parts  that  pull  on  the  cords.  These  parts  are  the 
muscles.  The  cords  are  the  tendons. 

What  the  Muscles  are  Like. — Not  only  are  the 
fingers  extended  and  bent  by  muscles  pulling  on  the 
tendons  which  are  tied  to  the  finger  bones,  but  when 


14      HOW  MOTIONS  IN   THE  BODY  ARE  PRODUCED 


Fig.  1. 

BICEPS  MUSCLE  ATTACHED  TO  THE  RADIUS. 


the  arm  is  bent  at 
the  elbow,  the  action 
is  accomplished  by 
a  muscle  in  the  up- 
per arm  pulling  on 
a  tendon  attached  to 
a  long  bone  in  the 
forearm. 

If  with  your  left 
hand  you  grasp  the 
right  upper  arm  while 
the  arm  is  being  bent, 

the  flesh  on  the  front  side  of  the  arm  will  be 
felt  to  swell  up  greatly. 

If  the  firigers  be  held  at  the  front  side  of 
the  elbow  while  the  arm  is  being  bent,  a 
very  large  cord,  the  tendon,  can  be  felt. 
The  swelling  flesh  is  a  large  muscle.  Fig.  i 
shows  the  arm  with  all  the  parts  removed 
except  the  bones  of  the  arm  and  this  muscle 
and  its  tendons  which  bend  the  arm.  Fig.  2 
shows  the  same  muscle  removed,  so  as  to 
better  show  its  appearance. 

Appearance  of  a  Muscle.  —  As  seen  in  the 
figure,  this  muscle,  which  is  called  the  biceps, 
has  a  thick  body,  tapering  off  at  each  end 
to  the  tendons.  The  thick  body  is  composed 
of  a  reddish  mass.  The  lean  part  of  the 
flesh  of  an  animal,  which  is  familiar  to  every 
one,  is  muscle. 

The    muscle    is    surrounded    by   a    tough     F-    2. 
membrane,    which    holds    all    of    its    parts     BICEPS. 


A   REVIEW   OF   THESE  POINTS  15 

together,  and  runs  off  toward  the  ends  of  the  muscle 
and  continues  into  the  tendon.  The  tendon  runs  to 
the  bone,  where  it  is  continuous  with  a  membranous 
covering  of  the  bone.  Thus  the  muscle  comes  to  be 
firmly  attached  to  the  bone. 

Action  of  the  Muscle.  —  It  has  already  been  seen 
that  when  the  hand  clasps  the  arm  over  the  biceps 
muscle  during  the  bending  of  the  arm,  it  is  felt  to 
swell  up  to  a  considerable  thickness.  If,  when  the 
muscle  is  in  action,  it  could  be  examined  with  the 
covering  of  the  arm  removed,  one  could  see  it  shorten 
as  well  as  thicken.  It  is  this  power  of  shortening 
and  thickening,  or  contracting,  as  it  is  called,  which 
enables  the  muscle  to  pull  the  bone  and  cause  the 
motion  of  the  arm. 

The  cause  of  the  motions  of  the  fingers  which  we 
observed  is  also  the  contraction  of  the  muscles.  In 
the  part  of  the  arm  just  below  the  elbow  is  a  num- 
ber of  muscles.  Each  one  is  smaller  than  the  bi- 
ceps, but  it  is  shaped  very  much  like  it.  Each  one 
ends  in  a  tendon  at  each  extremity,  the  one  toward 
the  elbow  being  short  and  attached  to  some  one  of 
the  bones  at  points  near  the  elbow  joint.  At  *the 
end  toward  the  hand  the  tendons  are  long,  some 
passing  to  the* wrist,  some  to  the  hand,  but  most  of 
them  passing  on  to  the  different  joints  of  the  fingers. 
Some  run  along  the  back  of  the  hand,  as  we  ob- 
served, and  some  on  the  palm  side. 

A  Review  of  these  Points.  — To  bend  a  finger,  we 
contract  a  muscle  in  the  forearm;  to  straighten  it, 
we  contract  another.  To  straighten  more  than  one 
finger,  as  in  reaching  for  an  object,  we  contract  sev- 


1 6      HO W  MOTIONS  IN   THE   BODY  ARE  PRODUCED 

eral  muscles  in  the  forearm;  to  bring  them  together 
on  the  object,  we  contract  several  others  in  the  same 
position.  To  bend  the  arm  at  the  elbow,  we  con- 
tract the  biceps.  We  may,  by  clasping  the  upper 
arm,  find  that  when  we  straighten  the  arm,  muscles 
on  the  opposite  side  from  the  biceps  contract  and 
pull  on  tendons  attached  to  the  forearm,  and  bring 
it  back  to  its  extended  position. 

Muscles  that  produce  Other  Motions  of  the  Arm.  - 
If  one  place  his  hand  at  different  positions  around 
his  shoulder  while  he  lifts  his  whole  arm  up,  brings 
it  forward,  backward,  downward,  or  in  any  other 
direction,  he  will  find  that  the  muscles  of  the  breast, 
of  the  top  of  the  shoulder,  or  of  the  back,  or  just 
below  the  shoulder,  are  acting.  These  muscles  are 
very  large  and  make  up  most  of  the  flesh  in  these 
regions.  Those  parts  which  lie  just  beneath  the  skin 
are  shown  in  Fig.  3,  but  still  others  lie  beneath  these. 

Other  Muscles  in  the  Body.  —  Whenever  any  mo- 
tion of  a  part  of  the  body  is  made,  it  is  by  the 
contraction  of  the  muscles.  To  produce  the  very 
many  motions  that  the  body  performs,  it  is  furnished 
wUh  about  five  hundred  muscles.  Figs.  3  and  4 
show  where  many  of  these  muscles  are  placed,  but  a 
very  large  number  lie  deeper  than  these  and  many 
are  small,  so  that  all  can  not  be  represented  at  once. 

Number  .of  Motions.  — The  five  hundred  muscles 
can  produce  more  than  five  hundred  motions,  for 
each  one  can  produce  a  motion  acting  alone,  a  still 
different  one  when  acting  with  another  muscle,  or 
even  with  several  other  -muscles.  For  example,  we 
may  carry  the  whole  arm  in  many  hundreds  of  dif- 


rig- 

FRONT  VIEV 


BODY. 


BACK 
PR.-I* 


Fig.  4, 

BODY. 


MUSCLES  IN   THE  LOWER  ANIMALS  if 

ferent  positions  with  but  a  limited  number  of  mus- 
cles, by  combining  their  contractions  in  different 
ways. 

Contractile  Power  of  Muscles.  —  The  power  oj 
contractility  which  the  living  muscle  has  is  the  source 
of  the  force  which  the  body  can  exert.  The  con- 
tractile muscular  substance  is  to  the  machinery  of 
the  human  body  what  the  steam  is  to  the  engine. 
It  is  well  known  that  hot  steam  presses  against  the 
walls  of  the  vessels  containing  it.  It  will  lift  the  lid 
of  a  kettle,  or  may  push  so  hard  as  to  burst  the  walls 
of  a  steam  boiler.  Men  take  advantage  of  this  great 
power,  and  let  the  steam  push  against  a  piston,  and 
by  its  connections 'turn  a  crank  which  makes  all  the 
motions  in  a  great  machine  shop. 

In  the  body,  the  muscular  substance,  instead  of 
pushing,  as  does  steam,  pulls  on  the  ends  of  the  ves- 
sels which  contain  it,  and  thus,  by  means  of  strings 
(tendons),  pulls  on  the  bones  and  makes  the  motions 
of  the  body. 

Muscles  in  the  Lower  Animals.  —  The  muscles 
in  the  common  animals,  such  as  horses,  dogs,  cats, 
rabbits,  and  the  like,  are  of  the  same  form,  and  are 
attached  to  bones  in  the  same  way  as  those  in  man. 
They  have  the  same  power  of  contracting  and  are  in 
every  respect  like  those  of  the  human  body. 

The  motions  of  all  animals,  except  certain  forms, 
chiefly  microscopic,  are  produced  by  muscles.  The 
muscles  of  the  higher  animals  are  arranged  in  about 
the  same  number  and  order  on  the  limbs  and  the 
remainder  of  the  body  as  in  man.  The  examination 
of  the  muscles  of  the  body  of  some  small  animal 

IND.  PR.  PHYS.  —  2 


1 8      HOW  MOTIONS  IN   THE  BODY  ARE  PRODUCED 

would  teach  very  clearly  how  the  muscles  appeal 
and  how  they  are  arranged  in  man,  and  how  the  ten* 
dons  attach  them  to  the  bones. 

What  causes  the  Muscles  to  Contract.  —  We  know 
that  we  can  cause  the  muscles  to  contract  whenever 
we  wish  to  do  so.  The  arm  can  be  moved  at  the  exact 
moment  and  with  just  the  force  we  desire.  It  is 
said,  for  example,  that  the  muscles  of  the  arm  are 
under  the  control  of  the  will.  If  the  arm  could  be  laid 
open  for  examination,  there  could  be  seen  some  other 
things  besides  muscles  and  tendons. 

Among  the  latter  would  be  seen  some  white  cords, 
which  divide  into  many  branches,  one  going  to  each 
muscle.  They  penetrate  the  sheath  of  the  muscle 
and  are  lost  in  its  substance.  These  cords,  divid- 
ing up  into  fine  threads,  are  nerves.  If  they  are  traced 
from  the  muscles,  they  are  found  to  run  up  the  arm, 
through  the  shoulder,  across  to  the  backbone,  and 
into  its  center.  Here  they  connect  with  a  large  nerve 
cord,  the  spinal  cord,  which  runs  to  the  brain.  These 
we  will  study  later,  but  mention  them  here  to  show 
that  the  muscles  are  connected  with  the  brain,  through 
which  the  will  acts. 

Now,  if  a  nerve  going  to  a  muscle  be  cut  in  two, 
then  no  power  of  the  will  can  make  it  contract.  It 
is  only  when  the  nerve  connects  the  muscle  with  the 
brain  that  we  can  move  the  muscle  when  we  wish  to. 
The  brain  can  send  some  influence  that  the  nerve  is 
able  to  conduct,  which,  when  it  reaches  the  muscle 
substance,  makes  it  contract.  The  exact  nature  of 
this  influence  is  unknown,  nor  is  it  known  how  it 
makes  the  muscle  contract.  This  influence  is  called 


VOLUNTARY  AND  INVOLUNTARY  MUSCLES       1 9 

a  nervous  Impulse.  The  nervous  impulse  in  some  way 
stirs  up  the  muscle,  or  excites  it  to  contract.  In 
physiology  this  is  called  stimulation  of  the  muscle. 
The  nervous  impulse  stimulates  the  muscle  to  con- 
traction. 

Voluntary  and  Involuntary  Muscles.  —  All  those 
muscles  whose  action  may  be  controlled  by  the  will 
are  called  'voluntary  muscles.  They  are  the  great 
majority  of  the  muscles  in  the  body.  The  muscles 
of  the  heart  and  of  the  stomach,  and  of  some  of  the 
other  organs,  are  stimulated  to  action  from  some 
other  source  than  the  .will,  and  the  will  can  not  con- 
trol them.  Consequently,  these  are  called  involun- 
tary muscles. 

Some  of  the  most  important  actions  of  the  body, 
such  as  those  in  the  circulation  of  the  blood,  in  breath- 
ing, and  in  the  digestion  of  food,  are  carried  on  by 
involuntary  muscles.  The  arrangement  by  which 
certain  muscles  may  act  independently  of  our  care 
and  attention  allows  important  actions  to  go  on 
while  we  are  asleep,  and  when  the  mind  is  so  occu- 
pied that  they  would  be  forgotten  or  neglected. 
Such  processes  as  circulation  and  respiration  require 
such  careful  regulation  to  get  them  just  right  for  the 
body  in  its  different  positions  when  it  is  active  or  rest- 
ing that  we  never  could  of  ourselves  manage  them 
properly.  The  involuntary  actions  relieve  us  of  the 
care  and  trouble  of  these  most  necessary  operations 
and  allow  us  to  give  our  time,  attention,  and 
strength  to  the  other  motions.  We  will  refer  to  this 
kind  of  action  again  when  we  study  the  nervous 
system. 


2O       CARE  AND  EXERCISE  OF  THE  MUSCLES 

CARE  AND  EXERCISE  OF  THE  MUSCLES 

We  have  just  seen  that  the  muscles  make  up  the 
greater  part  of  the  body.  They  do  the  work  of  the 
body  in  walking,  running,  working  in  field  or  shop,  or 
showing  activity  in  the  playground.  That  the  muscles 
be  kept  in  good  condition  is  of  the  greatest  importance. 
First,  because  we  wish  to  have  the  laboring  part  of 
the  body  in  good  working  order  so  that  all  that  it  has 
to  do  may  be  done  well.  Second,  because  if  so  large  a 
part  of  the  body  is  not  in  good  condition,  the  general 
health  of  the  body  is  seriously  affected. 

The  complete  care  of  the  muscles  would  demand 
'good  care  of  all  the  rest  of  the  body  because  all  the 
rest  of  the  body  either  directly  or  indirectly  affects 
the  muscles.  For  example,  the  respiration  furnishes 
the  muscles  with  oxygen  and  throws  away  their  car- 
bonic dioxide.  The  digestive  system  furnishes  them 
with  food.  The  circulation  sends  through  them  the 
blood  which  brings  the  food  and  oxygen  and  car- 
ries away  the  carbonic  dioxide.  The  nervous  system 
brings  them  the  stimulus  that  makes  them  contract, 
and  it  regulates  their  supply  of  blood. 

Other  parts  of  the  body  also  help  the  muscles,  and 
the  care  of  the  muscles,  as  we  have  just  said,  includes 
the  care  of  these  parts  as  well.  But  as  we  shall  speak 
of  the  care  of  these  parts  in  other  sections  of  this 
book,  we  will  consider  here  only  the  immediate  care 
of  the  muscles  themselves. 

First  of  all,  the  muscles  must  have  exercise  to  keep 
their  health.  If  an  arm  were  bound  so  that  no  part  of 
it  could  ever  move,  its  muscles  would  wither  away. 


EXERCISE  FOR   ADULTS  21 

But  if  the  muscles  of  the  arm  are  well  used,  they  grow 
in  size,  becoming  firm  and  strong.  What  is  true  of  mus- 
cles of  the  arm  is  true  of  all  the  other  muscles  of  the 
body.  They  must  work  to  keep  in  good  condition. 

Thus  the  first  law  of  health  is  that  we  must  take 
exercise.  It  is  plain  that  the  exercise  must  bring 
into  activity  all  the  muscles  of  the  body.  If  we  re- 
member these  two  facts,  we  need  have  no  trouble  in 
deciding  whether  any  form  of  exercise  is  good  or 
bad. 

Since  the  working  of  the  muscles  demands  an  abun- 
dance of  pure  air,  it  is  best  when  possible  that  the  exer- 
cise be  taken  out  of  doors.  If  the  weather  or  other 
conditions  require  that  it  be  taken  within  doors,  the 
rooms  must  be  well  ventilated,  or  much  of  the  benefit 
of  the  exercise  will  be  lost. 

Exercise  of  Children. — The  well-known  out-of-door 
games  are  all  good  forms  of  exercise,  because  they 
require  vigorous  use  of  the  muscles  of  all  parts  of  the 
body,  arms,  legs,  and  trunk.  They  also  train  the  sight, 
hearing,  and  touch  to  work  well  with  the  muscles,  for 
the  motions  must  be  guided  well  by  these  senses  or 
the  player  loses  the  game. 

The  helpful  work  on  the  farm  and  about  the  home 
are  all  good  forms  of  exercise.  Those  children  who  have 
opportunity  for  such  work  are  very  fortunate,  for  not 
only  do  they  get  necessary  exercise,  but  they  receive 
training  in  doing  useful  things  which  gives  them 
advantages  over  those  who  do  not  get  this  training. 

Exercise  for  Adults.  —  Those  people  whose  occupa- 
tions require  labor  of  the  body,  that  is,  constant  exer- 
cise of  the  muscles,  of  course  do  not  need  to  plan  for 


22          CARE   AND   EXERCISE    OF  THE  MUSCLES 

special  exercise.  They  need  mostly  rest  and  recrea- 
tion. But  those  whose  -occupations  do  not  require 
much  activity  of  the  muscles  need  special  provision 
for  exercise.  This  must  be  true  also  for  those  whose 
employment  requires  some  sort  of  work  bringing  into 
activity  only  a  limited  group  of  muscles.  An  example 
would  be  —  one  working  at  a  machine  which  requires 
only  a  single  hand  or  arm  to  be  active.  Another 
would  be  —  an  occupation  which  requires  keeping  the 
body  in  a  single  position  for  long  periods  of  time. 
For  such  people  there  are  two  kinds  of  exercise.  The 
one  includes  out-of-door  exercise  in  its  various  forms, 
the  other  the  different  forms  of  exercise  planned  for 
the  gymnasium. 

The  outdoor  sports  will  appeal  to  some,  while  oth- 
ers will  prefer  the  gymnasium.  Since  the  exercise  that 
gives  most  pleasure  is  most  beneficial,  the  most  pleas- 
ing form  may  be  chosen. 

Excessive  exercise,  or  overwork  of  the  muscles,  is 
injurious.  Necessity  may  sometimes  force  one  to 
overwork,  as  to  save  a  home  from  fire  or  flood,  or  to 
meet  some  other  unusual  condition.  One  may  become 
exhausted  from  such  excessive  work  and  recover  well 
from  it.  But  continuous  overwork  would  be  very 
harmful. 

To  sum  up.  Exercise  of  all  the  muscles  is  necessary 
for  good  health.  The  exercise  should  be  taken  in 
good  air.  It  should  be  sufficiently  frequent,  but  not 
excessive. 


CHAPTER  II 
SKELETON   OF   THE  UPPER  EXTREMITIES 

General  View.  —  Since  the  bones  of  the  arm  and 
hand  are  so  easily  traced,  and  their  uses  can  be  so 
clearly  made  out,  we  will  study  them  in  some  detail. 
The  bones  of  the  arm  illustrate  many  facts  about 
bones  in  general.  They  are  generally  grouped  as 
bones  of  the  hand,  the  forearm,  and  the  arm,  and 
are  attached  to  the  body  by  the  shoulder  girdle,  the 
whole  group  being  sometimes  referred  to  as  the  bones 
of  the  upper  extremities. 

The  Bones  of  the  Hand.  —  We  have  just  seen  that 
the  fingers  have  each  three  bones  and  the  thumb 
has  two  —  fourteen  in  all.  They  are  called  the  pha- 
langes, a  single  one  a  phalanx.  The  five  bones  which 
we  traced  in  the  palm  of  the  hand,  and  whose  outer 
ends  are  the  knuckles,  are  called  the  metacarpals. 

Notice  that  the  metacarpal  of  the  thumb  is  free  to 
move  in  many  directions,  while  those  of  the  fingers 
are  firmly  bound  together.  This  arrangement  allows 
the  thumb  to  be  brought  opposite  to  any  one  of  the 
fingers  or  to  most  points  on  the  palm.  This  power 
of  moving  the  thumb  so  freely  increases  very  greatly 
the  usefulness  of  the  hand. 

To  convince  one's  self  of  this,  let  him  attempt  to 
use  the  hand  without  using  the  thumb  in  picking  up 

23 


24       SKELETON   OF   THE    UPPER   EXTREMITIES 


objects,  and  in  handling  them,  and  then  in  contrast 

repeat   the  operations  with   the  help  of   the   thumb. 

While    the   fingers   without    the    thumb  may  become 

very  expert,  yet  the  thumb 
wonderfully  increases  the 
usefulness  of  the  whole 
hand. 

If  we  attempt  to  trace 
the  metacarpals  back  to- 
ward the  arm  by  feeling 
them  under  the  skin,  we 
soon  lose  them  in  the  flesh 
that  surrounds  them. 

Immediately  under  the 
skin  and  flesh  in  the  wrist 
we  can  feel  a  solid  portion. 
This  is  a  bunch  of  small 
bones,  eight  in  number, 
arranged  in  two  rows  of 
four  in  each  row.  They 

are  the  bones  of  the  wrist  and  are  called  the  car  pah. 

Compare  your  own  hand  with  the  picture  of  the  bones 

of  the  hand  shown  in  Fig.  5. 

Bones   of   the   Forearm.  —  That   part   of    the    arm 

between  the  wrist  and  the  elbow  joint  is  called  the 

forearm.     Immediately   back   of   the   wrist  joint    the 

ends  of  the   two  bones  may  be  felt  under  the  skin. 

The  end  of  one  makes   the  little  round  knob  which 

shows  under  the  skin  on  the  little-finger  side  of  the 

arm. 
This  is   the   end   of   the   ulna.    The   bone   may   be 

traced    for   its  whole    length,   and   will  be  found    to 


F.g.  5. 

BONES  OF  THE  HAND. 


MOVEMENTS   OF   THE  RADIUS 


extend  to  the  elbow  joint.     It  makes  the  point  of  the 
elbow  where  it  is  very  close  to  the  skin. 

By  the  side  of  this  bony  knob  of  the  ulna,  near  the 
wrist,  lies  the  end  of  the  radius.    The 
broad 'end  of  this  bone  fills  up  the  space 
from  the  knob  of  the  ulna  to  the  edge  of 
the  arm  on  the  thumb  side. 

It  is  this  broad  end  of  the  radius  to 
which  the  hand  is  joined  to  make  up  the 
wrist  joint.  Thus  the  radius  carries  the 
hand.  The  radius  may  also  be  traced 
to  the  elbow  joint. 

Movements  of  the  Radius.  —  If  the 
hand  be  held  out  with  the  palm  turned 
upward,  it  will  be  found  that  the  radius 
and  ulna  lie  side  by  side.  Now,  while 
the  arm  is  in  this  position,  turn  the 
hand  over,  so  as  to  bring  the  palm  down, 
and  during  this  motion  watch  the  motion 
of  the  two  bones  of  the  forearm.  It  will 
be  seen  that  the  radius  turns  over  the 
ulna  until  it  comes  to  lie  across  it. 

It  ends  at  the  elbow  in  a  little  shallow  cup  about 
three  fourths  of  an  inch  across,  which  fits  on  a  knob 
on  the  large  bone  of  the  arm.  This  cup-shaped  end  of 
the  radius  allows  it  to  turn  on  this  knob  as  on  a  point. 

A  groove  in  the  side  of  the  wrist  end  of  the  bone 
allows  it  to  slide  over  the  knob  of  the  ulna.  Now, 
muscles  are  so  arranged  that  they  can  quickly  pull 
the  radius  over  the  rigid  ulna;  and  as  the  radius  car- 
ries the  hand,  of  course  the  hand  is  turned  over. 
This  arrangement  is  for  turning  the  hand  over. 


Fig.  6. 

BONES  OF  THE 
FOREARM. 


26       SKELETON  OF  THE    UPPER   EXTREMITIES 


The  same  bones  in  a  dog's  foreleg  are  bound  firmly 
together,  and,  consequently,  it  can  not  turn  its  fore- 
paw  over;  but  in  the  cat's  foreleg  the  radius  has  a 
little  motion,  and  it  may  be  seen  that  while  the  kitten 
is  playing  with  a  ball,  it  will  often  turn  its  forepaw 
slightly. 

Now  examine  carefully  the  figures  of  the  ulna  and 
radius  given  here,  and  determine  which  parts  of  them 
you  can  trace  in  your  own  arm.  It  may 
be  remembered  from  the  lesson  on  mus- 
cles that  it  is  to  the  radius  that  the  biceps 
muscle  is  attached. 

The  Humerus.  —  In  the  part  of  the  arm 
between  the  elbow  and  the  shoulder  is  a 
very  large  bone  called  the  humerus.  A 
picture  of  this  bone  is  shown  in  Fig.  7. 

The  elbow  end  has  grooves  and  a  knob 
for  the  ulna  and  radius  to  fit  into.  The 
shoulder  end  is  formed  into  one  large, 
smooth,  round  end  to  fit  into  a  cup-shaped 
part  of  a  bone  at  the  shoulder,  called  the 
shoulder  blade. 

The    sides    of    the    broad    end    of    the 
humerus  are  very  prominent  at  the  elbow, 
but  the  shoulder  end,  called  the  head  of 
the  humerus,  is  so  deeply  buried  in  the 
large  muscles  which  move  the  arm  that 
it  can  not  be  so  well  examined. 
Scapula   and    Clavicle.  —  As   was    said,    the    round 
head  of  the  humerus  is  fitted  to  a  part  of  the  shoulder 
blade,  the  scapula  (seen  in  Fig.  8  ).    One  can  not  well 
make  out  the  whole  outline  of  this  bone  in  his  own 


Fig.  7. 

THE  HUMERUS. 


SCAPULA   AND    CLAVICLE 


shoulder,  but  he  may  easily  trace  it  in  that  of  another 
person. 

The  prominent  hard  part  felt  just  at  the  top  of  the 
shoulder  is  the  upper  end  of  the  ridge  which  runs 
across  the  bone.  This  ridge 
lies  near  the  skin,  and  can 
be  traced  across  the  bone 
to  its  posterior  edge,  where 
it  ends.  The  edges  of  the 
scapula  can  also  be  made 
out.  It  is  a  flat,  triangular 
bone  fitted  to  the  upper 
part  of  the  back.  Besides 
acting  as  a  support  to  the 
humerus,  it  serves  also  as  a 
place  to  which  are  fastened 
many  of  the  muscles  that 
move  the  arm. 

The  clavicle  is  the  collar 
bone.  It  is  very  near  the 
skin  at  the  front  part  of  the  base  of  the  neck,  and 
can  be  traced  from  the  shoulder  to  a  point  at  the  top 
of  the  front  part  of  the  chest.  Its  use  is  to  hold  the 
shoulders  and  arms  back  from  the  chest. 

The  clavicle  and  scapula  together  make  a  firm  brace 
to  support  the  arm  and  attach  it  to  the  body. 

Often  the  arm  is  called  upon  to  lift  a  heavy  weight, 
or  push  with  great  force  against  an  object.  These 
actions  would  be  impossible  if  the  arm  were  not 
thoroughly  braced  against  the  body.  The  scapula 
and  clavicle  make  this  brace. 

It  will  help  us  to  understand  the  uses  of  the  bones  if 


Fig.  8. 

THE  SCAPULA. 


28        SKELETON  OF   THE    UPPER  EXTREMITIES 


we  study  how  levers  are  used  outside  of  the  body.     A 
lever  is  a  rigid  rod  or  bar  used  in  three  ways.    Thus, 

one  end  of  it  may  be 
placed  under  a  stone 
to  be  lifted,  the  hand 
exerting  the  fcvrce 
downward  may  be 

placed  at  the  other 
Fig.  9. 

end,  and  the  support 

of  the   lever   somewhere  between    the   hand   and   the 

stone  (Fig.  9). 

Another  method  is  to  place  the  weight  to  be  lifted 

somewhere    between 

the  ends  of  the  lever, 

the    hand     exerting 

the  force  upward  at 

one    end,     and     the 

support  at  the  other 

end     of     the     lever 

(Fig.  ic). 

A  third  way  is  to  exert  the  force  upward  on  the  lever 

at  a  point  between  the  ends,  while  the  weight  is  at 

one  end  and  the  sup- 
port at  the  other 
(Fig.  u).  The  point 


Fig.  10. 


of  support  is  called 

the  julcrum.  We  can 
arrange  the  levers  in 
the  first  two  ways  so 
that  a  heavy  weight 

can  be  lifted  slowly  with  small  force  acting  quickly. 

In  the  last  way  we  can  get  a  weight  moved  quickly  by 


Fig.  11. 


THE   FORELIMBS   OF   THE   LOWER   ANIMALS       29 

a  large  force  acting  slowly.  Now  if  you  compare  the 
levers  with  Fig.  i,  representing  the  arm,  you  will  see 
that  the  forearm  is  a  lever  used  as  in  Fig.  n,  the 
muscle  acting  as  the  force,  the  elbow  as  the  support 
to  the  lever,  and  the  ball  as  the  weight  to  be  lifted. 
With  this  kind  of  a  lever,  although  the  muscle  moves 
somewhat  slowly  but  with  great  force,  the  hand  can 
move  very  quickly.  Quickness  of  motion  of  the 
hand  is  more  important  than  mere  strength  of  the 
movement.  Most  of  the  levers  of  the  body  are  of 
this  kind. 

The  Uses  of  the  Bones  of  the  Arm  and  Hand.  - 
Our  study  of  the  arm  has  shown  that  the  uses  of  the 
bones  of  the  arm  and  hand  are  three: 

1.  To  act  as  levers. 

2.  To  serve  as  fulcrums  to  pry  against. 

3.  To  furnish  places  for  the  attachment  of  muscles. 
Each  of   these   uses   is  concerned   with   the  move- 
ments of  the  arm. 

The  Forelimbs  of  the  Lower  Animals. — The  bones 
of  the  forelimbs  of  animals  which  have  backbones  — 
that  is,  mammals,  birds,  reptiles,  frogs,  and  fishes 
-  correspond  to  those  of  our  own  arm  and  hand. 

The  bones  in  the  foreleg  of  a  cat  are  very  much 
like  our  own.  The  clavicle  is  very  small,  and  there 
are  but  seven  carpals;  with  this  exception  the  bones 
are  all  present,  and  of  nearly  the  same  shape. 

As  different  as  the  foreleg  of  a  horse  or  of  a  cow 
appears  from  our  own  arm  and  hand,  a  comparison 
of  the  corresponding  bones  of  each  would  show  them 
to  be  remarkably  alike. 

The  wrist  bones  of  these  animals  are  at  the  joint 


30        SKELETON  OF   THE    UPPER  EXTREMITIES 

usually  known  as  the  "  knee."  The  hand  is  very 
narrow,  consisting  of  but  one  strong  bone  and  two 
slender  rudiments  of  bones  to  represent  the  meta- 
carpals,  and  with  but  one  finger  in  the  horse,  and 
four  fingers  in  the  cow  —  two  being  fully  developed, 
and  two  only  rudiments. 

Of  course,  we  call  these  the  feet  of  these  animals, 
but  they  correspond  exactly  to  the  last  joint  of  our 
fingers,  the  hoofs  being  the  nails. 

The  forelimbs  of  animals  differ  greatly  in  order  to 
fit  them  to  the  different  conditions  of  life  in  which 
we  find  them.  If  you  will  examine  why  this  is  true 
in  the  case  of  several  animals,  such  as  those  just 
mentioned,  and  also  of  others,  such  as  a  bird,  a  mole, 
a  squirrel,  a  rabbit,  a  sunfish,  or  a  frog,  the  study 
will  make  the  knowledge  of  your  own  arm  much 
clearer. 


CHAPTER  III 

THE    SKELETON.      HYGIENE    OF    THE    BONES    AND 
JOINTS 

The  Bones  of  the  Leg.  —  The  bones  of  the  leg 
correspond  very  nearly  to  those  of  the  arm.  In  the 
toes  the  number  is  the  same,  and  they  are  called  by 
the  same  name,  the  phalanges.  There  are  five  meta- 
tarsals,  in  place  of  the  metacarpals,  and  seven  tarsals 
in  the  instep,  which  corresponds  with  the  wrist. 


Fig.  12. 

SECTION  THROUGH  THE  BONES  AND   LIGAMENTS  OF  THE  FOOT.    THE  PARTS  OF 
THE  JOINTS  ARE  WELL  SHOWN. 

The  tarsals  are  of  larger  size  than  the  carpals, 
while  the  phalanges  of  the  foot  are  smaller  than 
those  of  the  hand.  In  Fig.  12  the  bones  of  the  foot 
are  shown  as  sawed  through.  This  shows  the  large 
tarsal  which  makes  the  heel  bone. 

31 


THE   BONES    OF  THE  LEG  33 

Just  above  this  bone  is  the  next  largest  tarsal, 
which  forms  a  joint  with  the  bone  of  the  lower  part 
of  the  leg.  In  this  figure  we  may  see  also  how  the 
tarsals  with  the  metatarsals  form  an  arch  of  bones  on 
which  the  weight  of  the  body  rests  in  standing. 

The  large  bone  of  the  lower  leg  resting  on  the  tarsal 
bone  is  the  tibia.  It  extends  from  the  instep  to  the 
knee,  where,  with  the  bone  above,  it  forms  the  knee 
joint.  By  the  side  of  the  tibia  lies  the  fibula,  a  long, 
slender  bone  firmly  attached  to  the  tibia. 

The  bone  in  the  thigh  is  the  femur.  It  is  the  largest 
bone  in  the  body.  The  end  at  the  knee  is  broad  and 
has  a  deep  groove  in  it,  while  at  the  upper  part  there 

is  a  turn  in  the  bone  which  then  ends  in  a  smooth  ball. 

• 

This  ball  of  the  femur  fits  closely  into  a  cup-shaped 
surface  on  the  hip  bone,  to  make  the  hip  joint.  The 
hip  bone,  or  os  innominatum,  as  it  is  named,  is  a  large, 
irregularly  shaped  bone.  It  comes  out  from  the 
central  line  of  the  body,  its  posterior  edge  joining 
firmly  to  the  backbone,  and  the  front  edge  being  also 
firmly  joined  to  the  corresponding  edge  of  the  hip 
bone  of  the  opposite  side.  Thus  we  see  that  the  hip 
bone  acts  as  a  strong  brace,  or  arch,  for  the  femur  to 
press  against. 

You  will  remember  that  the  bones  at  the  shoulder 
form  a  brace  for  the  arm  to  press  against.  The  brace 
at  the  hip  is  still  stronger,  as  it  must,  during  walking, 
bear  not  only  the  whole  weight  of  the  body,  but  also 
whatever  heavy  weights  one  may  carry.  If  the  leg 
be  straightened,  there  can  be  easily  detected  at  the 
knee  a  disk-shaped  bone  which  is  known  as  the  patella, 
or  kneecap. 

IND.  PR.  PHYS.  —  3 


34 


THE   SKELETON 


This  bone  is  embedded  in  a  large  tendon  which 
passes  over  the  knee  to  join  the  tibia.  The  patella, 
by  fitting  into  a  groove  on  the  end  of  the  femur,  helps 
the  tendon  work  over  the  bend  of  the  knee. 

Uses  of  the  Bones  of  the  Leg.  —  The  bones  of  the 
leg  are,  like  the  bones  of  the  arm,  mostly  used  as 
levers.  When  the  muscles  of  the  front  part  of  the 
thigh  contract,  they  pull  upon  the  tibia 
and  extend  the  leg ;  when  those  on  the 
opposite  side  contract,  they  bend  the  leg. 
Muscles  at  the  hip,  by  acting  .on  the 
femur,  may  pull  the  leg  in  various  direc- 
tions. 

A  large  muscle  in  the  calf  of  the  leg  is 
attached  by  a  very  large  tendon  to  the 
heel  bone.  This  is  shown  in  Fig.  14,  and 
can  easily  be  felt  under  the  skin  at  the 
heel. 

When  this  muscle  contracts  it  acts  on 
the  bones  of  the  foot,  which  are  bound 
firmly  together.  It  is  a  lever  of  the  sec- 
ond kind,  to  pry  up  the  body  resting 
on  it  by  the  tibia.  These  muscles  are 
all  used  in  the  leg  in  standing,  walking, 
and  running.  The  limbs  should  be 
studied  in  these  actions. 

The  Divisions  of  the  Body.  —  The  evi- 
dent parts  of  the  body  are  the  head,  the 
neck,    the    trunk,   and    the   limbs.     The 
Fig.  14.         limbs  —  the  arms  and  the  legs  —  are  to 
MUSCLES  AND  TEN-  be  thought  of  as  mere  appendages  of  the 
body  to   serve  its   demands.    The  legs 


A   VERTEBKA 


35 


carry  the  body  about,  and  the  arms  carry  to  it  what 
it  needs,  defend  it,  and  in  a  hundred  ways  attend  to 
its  wants. 

That  the  limbs  may  thus  act,   they  must  have  a 
firm  support  to  push  against.    The 
bony  arches  which  carry  them  find 
this  support  in  the  skeleton  of  the 
rest  of  the  body. 

The  Spinal  Column.  —  The  spinal 
column  consists  of  twenty-six  bones 
very  firmly  bound  together  into  one 
firm  beam.  Its  bones  are  twenty- 
four  Vertebrae,  the  sacrum,  and  the 
coccyx. 

The  vertebrae  are  divided  into 
three  groups:  'seven  in  the  neck,  the 
cervical  vertebrae;  twelve  to  which 
the  ribs  are  attached,  the  dorsal 
vertebrae;  and  five  in  the  loins, 
the  lumbar  vertebrae.  The  sacrum 
is  the  base  on  which  the  column 
of  vertebrae  stands,  and  serves  as 
the  place  for  the  pelvic  arch  to 
brace  against. 

A  Vertebra.  —  Each  vertebra  (Figs. 
16  and  17)  has  a  central  part  from 
which  extend  seven  projections, 
called  processes.  These  serve  for 
the  attachment  of  ligaments  by 
which  the  vertebrae  are  joined  in 
one  mass.  They  serve  also  for  the  attachment  of  many 
muscles  which  move  the  limbs  and  the  head,  and  ac- 


SPINAL  COLUMN. 


36  THE   SKELETON 

complish  other  motions.     Each  vertebra  has  an  open- 
ing  in   its   posterior   part.     When    the    vertebrae   are 
brought  into  line,  these  openings  make  a  tube,  called 
the  spinal  canal,  the  upper  part  of  which  contains  thev 
spinal  cord,  and  the  lower  part  many  nerves. 

Bones  of  the  Thorax.  — The  walls  of  the  chest  are 
supported  by  the  twelve  ribs  on  each  side,  the  ster- 
num or  breastbone  in  front,  and  the  dorsal  vertebras 
behind.  The  ribs  end  in  cartilages  in  front.  The 
cartilages  of  the  first  seven  are  joined  to  the  sternum; 


Fig.  16.  Fig.  17. 

A  DORSAL  VERTEBRA.     SIDE  VIEW.        VERTEBRA  SEEN  FROM  ABOVE. 

those  of  the  next  three  are  joined  together  and  to  the 
seventh;  the  last  two  are  free  or  "floating"  in  front. 

The  Skull. —The  skull,  the  skeleton  of  the  head, 
is  placed  on  the  upper  vertebra.  It  consists  of  the 
cranium  and  the  bones  of  the  face.  The  cranium  is 
the  part  that  incloses  the  brain.  As  felt  under  the 
scalp,  it  seems  to  be  one  spherical  bone,  but  it  is  really 
made  of  eight  pieces  which  are  so  nicely  joined  together 
that  the  joints  can  not  be  detected  until  the  bones  are 
exposed.  The  whole  eight  make  a  box,  with  several 
holes  in  the  floor. 

Bones  of  the  Face.  — These  are  fourteen  in  num- 
ber. The  only  one  free  to  move  is  the  lower  jaw 


THE    USES   OF  BONES 


37 


bone,  called  the  lower  maxillary.  This  bone  bears 
the  lower  teeth.  It  forms  a  joint  with  the  skull. 
It  is  drawn  upward  in  closing  the  mouth  by  muscles 
which  can  be  felt  in  the  cheeks,  and  is  drawn  down 
by  muscles  in  the  neck. 

The  Uses  of  Bones.  —  We  have  already  seen  that 
the  main  uses  of  the  bones  of  the  arm  and  leg  are 
for  levers,  or  for 
the  attachment 
of  muscles  to 
produce  motions. 

The  shoulder 
and  hip  bones  are 
for  the  attach- 
ment of  muscles, 
and  to  serve  as 
braces  for  the 
limbs  to  push 
against.  Many 
of  the  bones  of 
the  head  serve 
for  the  attach- 
ment of  muscles, 
which  make  it  possible  to  carry  the  head  erect,  and 
to  move  it  about. 

Some  of  the  bones  of  the  head  are  the  necessary 
place  of  attachment  of  muscles  to  move  the  lower 
jaw,  the  bone  of  the  lower  jaw  being  itself  a  lever 
with  motion  as  its  chief  purpose. 

The  spinal  column  is  the  main  region  for  the  attach- 
ment of  the  great  muscles  of  the  body,  and  is  at  the 
same  time  constantly  acting  as  a  lever.  The  ribs 


Fig.  18. 

BONES  OF  THE  HEAD. 


THE  SKELETON 


make  rigid  walls  to  a  part  of  the  body  to  act  as  the 
sides  of  a  bellows  in  breathing.  They  act  also  as  levers, 
both  in  taking  in  the  air  and  in  expelling  it  from  the 
lungs. 

The  skeleton,  then,  has  two  chief  functions:  to  fur- 
nish levers,  and  surface  for  the  attachment  of  muscles 
to  work  these  levers. 

Secondary  Uses  of  the  Bones.  —  Some  of  the  bones 
are  incidentally  used  for  protecting  parts  from  outside 
injuries,  as  in  the  case  of  the  bones  of  the  skull,  guard- 
ing the  brain,  and  the  bones  of  the  chest,  guarding 
the  heart,  while  they  perform  their  more  important 
functions  as  well. 

Different  Kinds  of  Skeletons.  —  All  those  animals 
which  have  a  spinal  column  are  called  vertebrates. 
Dogs,  cats,  horses,  cows,  squir- 
rels, birds,  frogs,  snakes,  and 
fishes  all  have  spinal  columns 
and  are  examples  of  vertebrates. 
But  in  animals  like  the  craw- 
fish, which  performs  vigorous 
motions  by  means  of  muscles, 
the  same  necessity  exists  for 
hard'  parts  to  act  as  levers,  and 
for  the  attachment  of  muscles. 
In  the  crawfish,  the  skin,  by 
becoming  a  rigid  crust,  only 
flexible  at  the  joints,  furnishes 
the  levers.  The  muscles  inside 
the  limbs  and  the  body 


Fig.  19. 


are 


A  CRAWFISH,  AN  ANIMAL  WHOSE 
SKELETON    is    THE    OUTSIDE 

SURFACE  OF  ITS  BODY  AND    attached  to  this  hard  crust,  and 
SJStSJSJ"    its  divisions  serve  the  same  pur- 


STRUCTURE    OF  A   BONE  AND    OF  A  JOINT       39 


pose  as  the  bones  of  man.    Thus  this  animal  wears  its 
skeleton  on  the  outer  surface  of  its  body. 

An  examination  of  the  crawfish  or  some  large  insect 
will  allow  the  arrangement  of  the  muscles  and  of  the 
outside  skeleton  to  be  much  better  understood. 

Animals  without  a  Skeleton.  —  There  are  animals 
without  a  skeleton  of  any  kind,  but  they  are  not  able 
to  accomplish  very  powerful  motions.  Most  of  them 
live  in  water,  by  which  they  are  partly  or  wholly 
held  up,  and  they  have  only 
slow  motions.  Most  of  these 
animals  are  very  small  and 
can  be  seen  only  by  the 
microscope. 

Some,  however,  that  live  in 
the  sea  are  of  considerable 
size.  Among  these  are  the 
jelly  fishes.  These  beautiful 
animals  can  swim  about  by  Fig.  20. 

Contracting  their  bell-Shaped      A  JELLYFISH,  AN  ANIMAL  WITHOUT 
i       f  mi      •      i       i*  £         A  FIRM   SKELETON.    IT   LIVES   IN 

bodies.    Their  bodies  are  of 

a  jellylike-looking  substance. 

They  get  along  well  enough 

as  long  as  they  are  floating 

in  the  water,  but  on  land  they  can  do  nothing  and  soon 

fall  to  pieces. 

Structure  of  a  Bone  and  of  a  Joint.  —  The  ex- 
amination of  a  fresh  joint  of  an  animal,  with  the 
bones  that  make  it,  would  best  teach  how  they 
are  formed.  A  joint  from  a  leg  of  mutton  would 
answer  well.  The  bone  is  made  up  of  a  hard,  solid 
portion  covered  over  with  a  thin  membrane.  The 


THE  SEA  AND  SWIMS  BY  CONTRACT- 
ING ITS  UMBRELLA-SHAPED  BQDY, 
WHICH  THROWS  THE  WATER  OUT 
OF  THE  HOLLOW  PLACE  ON  THE 
UNDER  SIDE  OF  ITS  BODY. 


40 


THE   SKELETON 


Fl9'21- 


center  of  a  leg  bone  is  filled 
with  marrow.  The  ends  of 
bones  which  go  to  form  the 
joints  are  enlarged  and  have 
roughened  places  on  them 
where  the  tendons  and  liga- 
ments are  attached.  Before 
cutting  into  the  joint  one  can 
see  how  it  is  covered  by  strings 
and  bands  of  membrane. 
Some  of  these  go  from  one 
bone  to  another  and  hold 
them  together.  Others  tie  the 
muscles  to  the  bone.  Those 


are  called  tendons,  and  those 

fastening  bones- to  bones  are  named  ligaments.  It  is 
these  which  are 
bruised  or  torn  in 
sprains  and  disloca- 
tions of  which  we 
shall  soon  speak. 

Fig.  2 1  shows  the 
human  shoulder 
joint  with  some  of 
the  ligaments  fas- 
tening the  bones 
together.  Fig.  22 
shows  the  human 
hip  joint  with  all 
ligaments  but  one 

,  HIP  JOINT,  WITH  LIGAMENTS  REMOVED,  EXCEPT  THE 

removed.  ONE  ON  THE  HEAD  OF  THE  FEMUR. 


HYGIENE    OF   THE   BONES  AND  JOINTS   •       41 

The  ends  of  the  two  bones  fit  together  very  nicely, 
and  are  covered  with  cartilage,  which  is  a  very  smooth 
and  a  very  elastic  substance.  Over  the  layers  of 
cartilage,  fastened  firmly  to  it,  is  a  membrane  which 
secretes  a  liquid  which  keeps  the  surfaces  of  the  joints 
moist. 

This  arrangement  allows  motion  with  the  least 
friction.  The  elasticity  of  the  cartilage  lessens  the 
jarring  effects  of  the  motions  of  the  body. 

HYGIENE  OF  THE  BONES  AND  JOINTS 

The  skeleton  and  its  parts  may  suffer  either  in  its 
growth  and  development,  or  by  injuries  coming  to  it 
by  accident,  as  in  broken  bones,  or  sprained  or  dis- 
located joints. 

As  the  skeleton  is  the  hardest  material  in  the  body, 
its  growth  determines  the  outline  of  the  form  and  size 
of  the  body.  Like  all  other  parts  of  the  body,  its 
growth  and  development  from  the  time  of  childhood 
to  that  of  full  growth  are  greatly  influenced  by  the 
food,  the  air,  and  the  exercise  it  receives.  Animals 
which  when  growing  have  been  poorly  fed  and  ill 
kept  in  general  have  smaller  or  less  vigorous  bodies 
throughout  life  than  they  would  otherwise  have 
possessed. 

It  is  the  same  with  man.  Measurements  taken  of 
large  numbers  of  children  living  in  conditions  where 
they  have  been  ill  fed  and  otherwise  poorly  cared  for, 
compared  with  those  of  children  better  fed,  show  the 
growth  of  the  better-fed  children  to  be  markedly 
greater. 


42          HYGIENE    OF   THE   BONES  AND  JOINTS 

The  skeleton  is  growing  from  birth  to  twenty  or  twenty- 
five  years.  This  is  a  slow  growth.  During  the  first  half 
of  that  time  the  bones  are  less  rigid  than  they  become 
later  on.  During  this  time  continuous  pressure  on  any 
of  them,  or  unnatural  positions  long  maintained,  may 
permanently  distort  or  misform  parts  of  the  bony  sys- 
tem. For  example,  a  habit  of  keeping  a  stooping  posi- 
tion in  the  growing  period  may  result  in  a  fixed  stoop 
that  can  not  be  changed.  Or  a  practice  of  sitting  in 
a  wrong  position  at  a  desk  or  in  a  chair  in  long  periods 
of  reading,  writing,  or  study  may  result  in  permanent 
distortion  of  the  body.  Continuous  pressure  of  cloth- 
ing on  the  ribs  may  result  in  misforming  the  chest. 
Pressure  of  badly  shaped  shoes  may  result  in  perma- 
nently malformed  feet.  If  it  is  desired  that  a  child 
should  grow  up  with  a  well-formed  body,  with  grace- 
ful carriage  and  movements,  the  parts  of  the  body 
must  be  kept  free  from  pressure,  wrong  positions  for 
long  periods  must  be  avoided,  and  habits  of  good 
positions  and  graceful  motions  must  be  continu- 
ously practiced;  for  as  the  skeleton  is  formed  so  it 
remains. 

We  have  seen  that  at  the  joints  the  bones  are  very 
firmly  bound  by  ligaments.  Yet,  a  sudden  twist 
which  may  occur  in  violent  action  may  bring  a  strain 
on  a  joint,  so  that  either  the  ends  of  the  bones  are 
slipped  past  each  other  or  the  ligaments  greatly 
stretched  or  partly  torn  and  bruised.  The  first  is 
called  a  dislocation  of  the  joint,  the  second  makes 
what  is  known  as  a  sprain. 

Of  course,  for  a  dislocation  a  skilled  physician  will 
be  called  to  place  the  parts  of  the  joint  back  in  their 


HYGIENE    OF  THE  BONES  AND  JOINTS          43 

proper  positions,  and  his  directions  for  the  care  of 
the  injured  joint  should  be  strictly  followed.  Other- 
wise a  permanent  distortion  might  result.  For  the 
trouble  of  a  little  intelligent  care  one  ought  not  to 
risk  having  a  lameness  or  disfigurement  for  the  rest  of 
one's  life,  to  say  nothing  of  impairing  the  usefulness  of 
a  part  of  the  body. 

In  both  a  dislocation  and  a  sprain  the  injuring  of 
the  ligaments  produces  great  pain,  and  the  parts  gen- 
erally require  considerable  time  in  healing.  In  severe 
cases  of  sprain  a  surgeon  should  be  consulted  as  soon 
as  possible,  as  some  serious  injury  may  be  present 
which  can  best  be  attended  to  before  much  inflamma- 
tion occurs.  If  the  sprain  is  not  very  severe,  it  needs 
only  rest.  If  it  is  painful,  bathing  in  warm  water 
may  allay  the  pain. 


CHAPTER   IV 

PARTS   OF   THE   CIRCULATORY   ORGANS 

The  Use  of  Blood.  —  We  have  long  known  that 
we  require  food  every  day,  and  that  water  and  air 
are  also  absolute  necessities. 

The  more  active  we  are,  the  hungrier  and  thirstier 
we  become,  and  the  more  food  we  actually  require. 
We  may  not  notice  that  we  use  more  air,  yet  it  is 
a  fact. 

What  is  the  cause  of  these  demands?  Just  for 
our  present  purpose  we  may  say  that  in  work  the 
body  consumes  the  food,  water,  and  air,  and,  in  con- 
sequence, there  must  be  a  further  supply  of  these 
substances.  When  we  say  that  the  body  needs  these, 
we  mean  nothing  more  than  that  the  parts  of  the 
body  need  them  —  that  is,  the  muscles,  the  bones,  the 
nerves,  and  the  like.  Further*  since  work  causes 
an  increased  demand,  it  must  be  the  parts  that  are 
working  most  that  are  most  in  need  of  the  food. 
Those  organs  are  the  muscles,  but,  of  course,  many 
other  parts  work  with  them. 

Now,  we  know  that  the  food  we  eat  does  not  go 
to  the  muscles  in  the  form  in  which  we  see  it.  The 
food  of  the  muscles  and  of  the  other  parts  of  the 
body  is  the  blood. 

44 


HOW  DOES    THE   BLOOD   EXIST  IN    THE   HAND?     45 

They  live  upon  the  blood,  which  is  formed  from 
the  food,  the  water,  and  a  part  of  the  air,  the  gas 
oxygen.  The  muscles,  the  nerves,  and  indeed  every 
tissue  in  the  body  gets  its  food,  drink,  and  oxygen 
from  the  blood.  When,  then,  we  take  more  food  or 
drink,  or  breathe  faster,  it  is  to  add  more  food,  water, 
or  air  to  the  blood  to  take  the  place  of  what  the  tis- 
sues of  the  body  have  used  in  the  work. 

How  the  blood  receives  the  supply  of  food  and 
drink  we  take,  and  how  its  supply  from  the  air  is  ob- 
tained, we  shall  study  later  in  the  chapters  on  Diges- 
tion and  Respiration.  At  this  place  we  shall  study 
the  blood  and  its  motion  through  the  body. 

The  Blood  in  the  Hand.  — The  hand  may  answer 
again  as  a  beginning  point  for  our  study.  Many 
accidents  have  taught  every  one  that  the  hand  is  full 
of  blood.  If  it  is  pierced  at  any  point,  even  with  a 
very  fine  needle,  the  blood  will  flow  from  it,  the  only 
exceptions  being  the  very  thin  outer  layer  of  the 
skin,  the  epidermis,  and  the  nails. 

How  does  the  Blood  exist  in  the  Hand?  —  It  might 
be  supposed  from  the  experiments  with  the  needle 
that  the  blood  is  in  the  hand  as  water  may  be  in 
a  sponge,  but  it  can  easily  be  shown  that  such  is 
not  the  case.  If  the  hand  is  allowed  to  hang  down 
quietly  for  a  short  time,  and  the  back  is  observed,  a 
network  of  ridges  of  a  bluish  color  will  appear  under 
the  skin,  and  the  whole  hand  will  be  of  a  deeper  pink 
color.  Now,  if  the  hand  be  held  above  the  head, 
it  will  be  observed  that  this  network  will  become 
very  much  less  prominent,  if,  indeed,  it  does  not 
entirely  disappear.  The  network  of  ridges  consists 


46  PARTS   OF   THE    CIRCULATORY   ORGANS 

of  tubes  which  are  carrying  the  blood  from  the  hand. 
When  the  hand  is  held  down,  the  blood  in  them  has 
to  flow  uphill,  and  consequently  the  tubes  all  be- 
come well  filled  with  the  liquid.  The  pink  color 
shows  that  the  rest  of  the  hand  has  more  blood  in 
it. 

Now,  when  the  hand  is  held  up  the  blood  runs  out 
of  these  tubes  better,  and  they  are  left  nearly  empty. 
There  is  less  blood  left  in  the  rest  of  the  hand  also. 
To  show  that  the  blood  is  flowing  from*  the  hand 
toward  the  shoulder,  one  can  press  the  blood  out  of 
the  tubes  of  the  back  of  the  hand  and  watch  them  fill 
again.  They  will  always  be  seen  to  fill  from  the  direc- 
tion of  the  fingers. 

How  does  the  blood  get  into  the  hand?  Find  the 
place  above  the  wrist  where  you  can  feel  the  beating 
of  the  pulse.  It  is  just  between  the  skin  and  the 
end  of  the  radius.  This  beating  is  in  one  of  the  tubes 
which  bring  blood  to  the  hand.  That  the  blood 
is  coming  from  the  shoulder  to  the  hand  can  be  proved 
by  pressing  firmly  on  the  tube  until  it  is  closed;  and 
then  it  will  be  found  that  the  stroke  of  the  beat  is  on 
the  shoulder  side  of  the  wrist. 

The  Names  of  the  Tubes.  —  The  blood  is  running 
along  this  and  other  tubes  deeper  in  the  arm,  on 
its  way  to  the  hand.  These  tubes  are  called  arteries. 

As  the  blood  flows  to  the  hand,  the  arteries  divide 
into  many  branches  which  become  smaller  as  they 
branch.  These  go  to  the  muscles,  bones,  and  skin, 
which  they  penetrate,  and  in  which  they  finally  branch 
off  until  they  are  so  minute  that  they  can  not  be  seen 
without  a  microscope.  These  very  fine  divisions  of  the 


THE  BLOOD  IN  OTHER  PARTS   OF  THE   BODY      47 

tubes  are  the  capillaries.  They  are  very  numerous, 
making  an  extremely  fine  network,  which  brings  the 
blood  to  even  the  minutest  divisions  of  the  muscles, 
bones,  etc. 

This  network  of  capillaries  soon  unites  its  vessels 
into  larger  and  larger  ones,  which  leave  the  muscles, 
bones,  and  other  parts  in  the  same  way  that  the  art- 
eries enter  them. 

These  returning  tubes  are  the  veins.  The  smaller 
veins  join  into  larger  and  larger  ones,  some  of  which 
we  have  observed  on  the  back 
of  the  hand.  Fig.  23  shows 
how  they  appear  in  some  tis- 
sues. The  picture  represents 
them  with  all  the  tissues  re- 
moved from  the  blood  vessels. 
The  largest  white  vessel  may 
represent  the  smallest  artery, 
which  is  divided  up  to  form 
the  network  of  capillaries,  RELATIONS  OF  ARTER  VEIN>  AND 
and  the  dark  vessel  the  CAPILLARIES. 

small  vein  with  the  returning  blood.  To  sum  up 
what  has  just  been  learned  of  the  hand,  it  may  be  said 
that  the  blood  comes  into  it  by  arteries  which  divide 
until  they  finally  become  capillaries,  which  are  in  every 
part  except  the  nails  and  the  outside  layer  of  the  skin, 
and  from  the  capillaries  it  returns  by  means  of  veins. 

The  Blood  in  Other  Parts  of  the  Body.  —  What 
has  just  been  learned  of  the  hand  is  true  for  every 
other  part  of  the  body.  To  every  part  arteries  are 
distributed,  ending  in  capillaries  which  join  to  form 
veins. 


48 


PARTS   OF   THE    CIRCULATORY   ORGANS 


RA 


When  the  hand  hangs  down,  the  blood  in  the  veins 
must  be  pushed  uphill  with  great  force  the  length  of 
the  arm.  When  the  hand  is  held  above  the  head,  the 
same  must  be  done  in  the  arteries.  If  the  arteries 
and  veins  were  exposed  to  view,  we  could  see  them 
running  up  the  arm,  past  the  shoulder,  across  the 
upper  part  of  the  chest,  and  finally  ending  in  the 
heart.  The  general  view  of  the  arteries  is  shown  in 
Fig.  26. 

The    Heart.  —  The   heart   is   a    force    pump   which 
night   and   day   pumps    the    blood    into    the    arteries 
with  enough  force  to  send  it  on 
through  the  capillaries  and  back 
to  itself  through  the  veins. 

The  heart  is  in  the  lower 
part  of  the  cavity  of  the  chest. 
It  is  somewhat  of  the  shape  of 
a  cone,  with  the  point  turned 
down  and  a  little  to  the  left, 
with  the  broad  end  turned 
toward  the  right  shoulder. 
The  heart  is  about  the  size  of 
the  person's  fist. 

The  position  of  the  point  or 
apex  of  the  heart  is  easily  de- 

.11  11 

termmed  by  the  beats  it  makes 
against  the  side  of  the  chest,  beween  the  fifth  and 
sixth  ribs,  a  little  to  the  left  of  the  central  line. 

If  the  open  hand  be  laid  on  the  chest,  so  that  the 
tip  of  the  middle  finger  is  at  the  point  where  the 
beats  are  felt,  and  the  wrist  is  turned  toward  the  right 
shoulder,  the  hand  will  be  over  the  heart. 


LV 


Fig.  24. 

THE  HEART. 
RA ,   right    auricle  ;    Rl',  right 


left  ventricle. 


,  left  auricle  ; 


THE    VESSELS   CONNECTING    WITH   THE  HEART    49 


PA 


PA 


The  Interior  of  the  Heart. — The  heart  is  divided 
into  four  rooms,  two  at  the  broad  (upper )  end,  the 
auricles  (Fig.  25  ),  and  two  below  these,  in  the  nar- 
rower end,  the  'ventricles.  There  is  a  partition  between 
the  auricles,  and  one 
between  the  ventricles. 
The  auricles  and  ven- 
tricles are  distinguished 
as  right  and  lejt. 

Between  each  auricle 
and  the  ventricle  below 
it  are  flaps  composed 
of  a  strong  membrane. 
These  flaps  are  arranged 
as  valves,  which  lie 
against  the  ventricles 


-    LV 


RV 


when  the  blood  passes 
from  the  auricles  to  the 
ventricles;  but  on  an 


Fig.  25. 

DIAGRAM  OF  THE  HEART. 

'A,    pulmonary    a 
>;    FC/and  VCS, 


A,    aorta;     PA,    pulmonary    artery;    P, 
pulmonary  veins;    KC/and  l/'CS,  vena  cava 

.      ,        ,  ,          ,  inferior  and  vena  cava  superior;    71,  tricuspid, 

attempt    OI    the    blOOd    tO      and  M,  mitral  valve.     The  other  letters  same 
.    ,  as  in  preceding  figure. 

return   to   the   auricles, 

these  valves  are  closed  by  the  current.  They  are 
shown  closed  in  Fig.  25.  The  one  on  the  right  side, 
the  tricuspid  valve,  consists  of  three  flaps,  the  one  on 
the  left,  the  mitral  valve,  consists  of  two  flaps.  There 
are  also  valves  at  the  origin  of  each  of  the  large 
vessels  leaving  the  heart,  called  semilunar  valves. 

The  Vessels  connecting  with  the  Heart.  —  From 
the  left  ventricle  there  arises  a  large  artery,  the  aorta, 
whose  branches  are  distributed  to  all  parts  of  the 
body. 

From    the   right   ventricle    there    arises   an   equally 

IND.  PR.  PHYS. — 4 


5O          PARTS   OF  THE   CIRCULATORY  ORGANS 

large  vessel,  the  pulmonary  artery.  Its  divisions  go 
to  the  lungs. 

Opening  into  the  right  auricle  are  three  large  veins: 
the  superior  vena  cava,  which  receives  blood  from  the 
veins  coming  from  the  head,  the  neck,  and  the  arms; 
the  inferior  vena  cava,  which  receives  the  blood  com- 
ing from  the  legs  and  most  of  the  trunk;  and  the 
vein  from  the  heart  itself,  the  coronary  vein. 

Opening  into  the  left  auricle  are  four  pulmonary 
veins,  bringing  blood  from  the  lungs. 

The  Aorta  and  its  Divisions.  —  The  aorta,  as  soon 
as  it  leaves  the  heart,  makes  a  turn  called  the  arch  of 
the  aorta,  and  passes  down  just  in  front  of  the  spinal 
column.  It  gives  off  branches  at  the  very  start  from 
the  heart,  and  along  its  whole  course.  These  branches 
subdivide  and  go  to  each  part  of  the  body,  where 
they  end  in  capillaries,  as  we  have  learned  in  the 
study  of  the  hand.  Trace  them  in  Fig.  26,  represent- 
ing the  arteries. 

The  Veins.  —  After  the  blood  is  gathered  up  by 
the  small  veins  it  returns  by  a  number  of  larger  veins, 
which  correspond  in  their  distribution  generally  in 
each  part  of  the  body  to  the  arteries. 

Structure  of  the  Heart. — The  walls  of  the  heart 
are  made  up  of  muscular  tissue.  The  valves  are  of 
connective  tissue.  There  is  a  connective-tissue  layer 
covering  the  heart.  A  sac  called  the  pericardium 
surrounds  the  heart.  Between  it  and  the  heart 
is  a  liquid  known  as  the  pericardial  liquid.  This  ar- 
rangement allows  the  heart  to  beat  with  as  little 
friction  as  possible.  The  walls  of  the  ventricles  are 
much  thicker  than  those  of  the  auricles,  those  of  the 


Fig.  26. 

DISTRIBUTION  OF  THE  ARTERIES. 


THE  DIVISIONS   OF   THE    CIRCULATORY  SYSTEM    51 


left  ventricle  being  thicker  than  those  of  the  right. 
The  greater  amount  of  work  done  by  the  left  ventri- 
cle requires  this. 

Structure  of  the  Blood  Vessels. — The  arteries 
have  strong  walls  of  connective  tissue,  with  some 
muscular  fibers,  especially  in  the 
small*arteries.  The  connective  tis- 
sue is  largely  of  the  elastic  variety, 
so  that  the  walls  of  the  arteries  will 
stretch  like  rubber. 

The  'veins  have  much  thinner 
walls,  which  are  mainly  of  inelastic 
connective  tissue,  and  consequently 
they  will  not  stretch.  The  small 
veins  have  some  muscular  fibers  in 
their  walls.  Many  of  the  veins  have 
valves  in  them,  formed  by  pouches 
of  connective  tissue,  which  allow 
blood  to  pass  toward  the  heart  but  prevent  it  from 
going  the  other  way. 

The  capillaries  have  extremely  thin  walls. 

The  Divisions  of  the  Circulatory  System.  —  The 
aorta,  its  branches  and  their  subdivisions,  the  capilla- 
ries into  which  they  empty,  and  the  returning  veins 
that  empty  into  the  right  auricle,  are  known  as  the 
vessels  of  the  systemic  circulation.  The  pulmonary 
arteries,  the  capillaries  of  the  lungs,  with  the  pulmo- 
nary veins,  are  the  vessels  of  the  pulmonary  circula- 
tion. 


Fig.  27. 

A  VEIN  LAID  OPEN, 
SHOWING  ITS  VALVES. 


CHAPTER   V 

THE     PHYSIOLOGY     OF     THE     CIRCULATORY     ORGANS. 
THE  BLOOD.       HYGIENE  OF  THE  CIRCULATION 

The    Course    of    the    Blood    in    Circulation.  —  The 

course  of  the  blood  in  circulation  is  represented  in 
the  diagram  in  Fig.  28.  This  shows  how  the  heart 
is  a  double  pump,  one  portion  being  placed  in  each 
of  the  systems  of  circulation,  the  pulmonary  and 
systemic. 

As  the  valves  are  shown,  the  blood  can  flow  but 
one  way,  and  before  completing  the  circuit  must  pass 
through  the  heart  twice.  It  must  also  pass  through 
at  least  two  sets  of  capillaries,  —  those  of  the  lungs 
(pulmonary  capillaries ),  and  those  of  some  other  part 
of  the  body  (systemic  capillaries). 

We  may  now  consider  the  action  of  each  part  of 
the  circulatory  system. 

The  Action  of  the  Heart.  —The  blood  flows  gently 
from  the  large  veins  into  the  auricles,  and  these  throw 
the  blood  into  the  ventricles  with  enough  force  to 
dash  it  up  their  sides,  as  water  dashes  up  the  sides  of 
a  glass  when  poured  into  it.  This  action  not  only  fills 
the  ventricles,  but  closes  the  valves  between  the  auri- 
cles and  ventricles. 

52 


THE  BLOOD  IN  THE  ARTERIES 


53 


Then  the  ventricles  immediately  contract  and  force 
the  blood  past  the  semi- 
lunar  valves, — the  right 
ventricle  into  the  pul- 
monary artery,  and  the 
left  ventricle  into  the 
aorta.  The  heart  is  a 
very  active  pump,  mak- 
ing about  seventy- two 
strokes  a  minute. 

The  Blood  in  the  Ar- 
teries. —  The  pulse  felt 
near  the  wrist  is  caused 
by  the  shock  given  to 
the  blood  in  the  arteries 
by  the  beat  of  the  left 
ventricle. 

The  capillaries  are  so 
small  and  numerous 
that  their  walls  make  a 
very  large  surface  for 
the  blood  to  flow  over. 
The  friction  from  this 
surface  is  great  enough 
to  hold  the  blood  back. 
As  the  heart  keeps  up 
the  pumping,  the  ar- 
teries become  so  full  of 
blood  that  their  elastic 
walls  are  stretched  to 
give  it  room. 

Every  time  the  heart 


Fig.  28. 

DIAGRAM  OF  THE  COURSE  OF  THE  BLOOD. 

RA,  right  auricle;  RV,  right  ventricle;  LA 
and  LV,  left  auricle  and  left  ventricle;  VCf 
and  yCS,  vena  cava  inferior  and  superior; 
Ao,  aorta;  Lgt  lungs;  A  I,  alimentary  canal; 
Lr,  liver;  VP.  portal  vein;  Ly,  lymphatics; 
Th  D,  thoracic  duct;  Let.  lacteals;  HA  and 
HV,  hepatic  artery  and  vein» 


54     PHYSIOLOGY  OF  THE   CIRCULATORY  ORGANS 

beats,  the  walls  of  the  whole  system  of  arteries  spring 
out.     It  is  this  that  we  feel  in  the  pulse. 

Pressure  of  the  Blood  in  the  Arteries.  —  By  being 
held  back  at  the  capillaries  and  forced  on  at  the 
heart,  the  walls  of  the  arteries  stretching  to  receive 
it,  the  blood  becomes  so  crowded  in  the  arteries  that  if 
an  artery  is  accidentally  opened  the  blood  spurts 
from  it  with  great  force.  This  condition  of  the  blood 
in  the  arteries  is  like  that  of  water  in  a  reservoir;  it 
is  under  pressure. 

The  Blood  in  the  Veins.  —  In  the  veins  the  blood 
flows  by  a  steady  stream,  very  slowly  in  the  small- 
est veins,  and  gradually  quickening  toward  the  heart. 
If  a  vein  be  opened,  the  blood  flows  from  it,  but  with 
little  force.  It  is  not  under  very  much  pressure  in 
the  veins. 

The  Use  of  the  Blood  Pressure  in  the  Arteries.  - 
The   advantages   of   the   arrangement    just   discussed 
are: 

First.  While  the  blood  is  thrown  out  from  the 
heart  in  jerks,  it  will  flow  into  the  capillaries  in  a 
steady  stream.  The  pulse  gradually  decreases  in 
force  from  the  heart  to  the  capillaries,  where  it  dis- 
appears. This  is  a  very  important  advantage.  The 
walls  of  the  capillaries  must  be  thin  to  allow  the 
blood  to  soak  through  them  to  the  tissues.  Thin 
walls  could  not  endure  a  stream  of  strong  jets  with- 
out breaking. 

Second.  As  the  blood  is  under  pressure  on  the 
arterial  side,  and  under  little  or  no  pressure  on  the 
venous  side,  the  amount  of  blood  going  to  any  or- 
gan may  be  regulated  by  widening  or  narrowing  the 


ACTIONS  OF  THE    CIRCULATORY  ORGANS        55 

arteries  going  to  it.  The  muscular  substance  in  the 
walls  of  the  small  arteries  does  this  by  contracting  or 
relaxing. 

This  advantage  is  just  as  important  as  the  first 
given,  for  without  it  there  would  be  no  means  of 
regulating  the  supply  of  blood  to  each  of  the  organs. 
All  parts  would  receive  blood  equally  at  all  times, 
whether  they  needed  it  or  not. 

The  Action  of  the  Capillaries.  —  It  may  be  re- 
called that  the  blood  supplies  the  tissues  with  food, 
water,  and  oxygen  from  the  air;  but  this  is  not  all 
that  the  blood  does.  It  also  takes  away  from  the 
tissues  certain  substances  which  they  in  their  ac- 
tivity are  constantly  making,  and  which,  if  they 
remained  in  the  tissues,  would  be  very  injurious  to 
them. 

Now,  the  changes  between  the  blood  and  the  tis- 
sues can  take  place  only  through  the  very  thin  walls 
of  the  capillaries.  The  liquid  part  of  the  blood,  and 
whatever  may  be  dissolved  in  it,  can  soak  through 
the  thin  walls  of  the  capillaries,  and  the  substances 
dissolved  in  the  liquid  part  of  the  tissues  may  soak 
through  in  some  way  to  the  blood,  which  carries 
them  along  in  its  current  to  be  disposed  of  elsewhere 
by  processes  to  be  described  in  other  chapters. 

Then  it  may  be  said  that  all  the  changes  between 
the  blood  and  the  tissues  take  place  in  the  capillaries, 
and  that  the  object  of  the  other  parts  of  the  circula- 
tory system  is  to  drive  the  blood  continually  through 
the  capillaries. 

Regulation  of  the  Actions  of  the  Circulatory  Organs.  — 
The  heart  is  composed  of  involuntary  muscles  and  can 


56        PHYSIOLOGY  OF  THE  CIRCULATORY  ORGANS 

not  be  influenced  by  the  will,  but  its  rate  of  beating 
is  often  changed  to  suit  the  needs  of  the  body.  If  one 
counts  his  pulse  before  performing  some  vigorous 
exercise,  and  again  a  short  time  after  he  has  begun 
it,  he  will  find  the  pulse  in  the  latter  case  more  fre- 
quent. The  heart  has  been  stimulated  by  its  nerves 
to  greater  action. 

At  the  same  time,  in  the  parts  of  the  body  that 
are  in  action  the  small  arteries  dilate  a  little  by  relax- 
ing their  muscular  walls.  This  allows  a  greater  amount 
of  blood  to  flow  into  them.  When  any  part  is  not 
in  vigorous  action,  small  arteries  which  furnish  it 
with  blood  contract  their  walls  and  lessen  the  supply. 

These  actions  are  regulated  by  nerves  in  a  way  to 
be  studied  when  we  come  to  the  nervous  system. 

Properties  of  the  Blood.  —  The  blood  is  familiar 
to  every  one  as  a  bright  red  liquid.  The  shade  of  red 
varies  in  the  body  from  the  bright  red  to  a  very  dark 
red.  Seen  through  the  thin  walls  of  the  veins,  it 
appears  blue. 

The  microscope  shows  that  the  blood  is  com- 
posed of  a  nearly  transparent  liquid,  in  which  is 
suspended  a  cloud  of  immense  numbers  of  little 
particles. 

The  liquid  is  plasma,  and  the  particles  are  blood 
corpuscles. 

Blood  Corpuscles.  —  There  are  two  kinds  of  blood 
corpuscles  —  the  red  and  the  white. 

The  red  corpuscles,  when  very  greatly  magnified, 
are  seen  to  be  thin  round  disks  with  slightly  concave 
sides.  They  are  about  3^Vo  °^  an  ^nc^  *n  diameter. 
Although  they  are  called  red  corpuscles,  their  color 


CO  A  G  ULA  TION  5  7 

is  but  a  faint  yellow.     It  is  only  in   great   numbers 
that  they  give  the  mass  the  appearance  of  red. 

They  differ  somewhat  in  shape  and  size  in  different 
animals.  Fig.  29  shows  the  ap- 
pearance of  the  red  corpuscles 
from  the  human  blood,  and  Fig. 
30  those  from  the  blood  of  a  frog. 
The  white  corpuscles  are  few  in 
number  compared  with  the  red. 
They  are  colorless  and  of  irregu- 
lar Shape.  HUMAN  RED  BLOOD  CORFUS- 

The  Use  of  the  Red  Corpuscles.  CIES"  HlGHLY  MAGNIFIED- 
—  The  red  corpuscles  in  the  lungs  take  up  oxygen, 
one  of  the  gases  of  which  the  air  is  composed,  and 
carry  it  to  the  tissues,  which  require  oxygen  constantly. 
The  Plasma.  —  The  liquid  part  of  the  blood  is  very 
complex.  It  is  receiving  water  and  digested  food 

from  the  digestive 
system  all  the  time, 
and  various  substances 
which  the  tissues  are 
constantly  producing. 
It  is  very  evident  that 
the  blood  must  have 

^^         dissolved  in  it  all  the 
Fig.  30. 

BLOOD  CORPUSCLES  OF  A  FROG.     HIGHLY  MAG-   SUbstanC6S    Which    are 

N1FIED-  required  for  the  growth 

of  the  tissues,  as  they  have  no  other  source  of  supply. 
Coagulation.  —  Soon  after  the  blood  is  taken  from 
the  blood  vessels  it  has  the  power  to  form  into  a 
mass  which  has  the  appearance  of  jelly,  called  clot. 
This  process  is  called  coagulation.  This  is  accom- 


58  HYGIENE    OF   THE    CIRCULATION 

plished  by  some  substances  which  are  always  in  solu- 
tion in  healthy  blood.  But  the  moment  that  the 
blood  comes  in  contact  with  some  other  body  than 
the  uninjured  wall  of  the  blood  vessel,  these  sub- 
stances form  into  very  fine  threads  throughout  the 
whole  mass  of  the  blood,  holding  the  corpuscles  en- 
tangled in  their  network. 

HYGIENE  OF  THE  CIRCULATION 

In  studying  the  hygiene  of  the  circulation  we  have 
to  consider  the  blood  on  the  one  hand  and  the  ma- 
chinery for  circulating  it  on  the  other  hand.  Since 
we  must  rely  on  the  blood  to  supply  every  part  of  the 
body  constantly  with  oxygen  and  food,  and  to  carry 
away  its  wastes,  it  is  of  the  greatest  importance  that 
the  circulatory  system  be  in  the  best  condition  possible. 

Good  Blood.  —  Good  blood,  then,  depends  on  good 
food  supplied  to  the  digestive  system,  and  on  a  good 
condition  of  that  system  so  that  the  food  may  be  prop- 
erly prepared  and  handed  over  to  the  blood.  But  it 
depends  also  on  pure  air  and  the  proper  working  of 
the  lungs ;  and  further  on  the  working  of  the  skin  and 
kidneys  that  get  rid  of  certain  wastes.  The  care  of 
the  blood  may,  therefore,  be  studied  in  detail  in  con- 
nection with  the  organs  by  which  it  is  affected. 

Germs  of  Disease.  —  The  blood  is  good  food  not 
only  for  the  cells  of  the  body,  but  also  for  many  germs 
of  disease,  which  are  living  microscopic  animals  or 
plants  that  sometimes  enter  the  blood.  And  since 
the  blood  circulates  to  every  part  of  the  body,  these 
germs  may  be  carried  along  and  give  rise  to  various 


USES   OF  COAGULATION  59 

forms  of  disease.  Some  of  these  will*  be  spoken  of 
in  another  place  at  greater  length.  (See  Chapter 
XIX.) 

Dangers  of  a  Wound.  —  Thus  it  happens  that  a 
wound  is  dangerous  not  only  because  of  the  loss  of 
blood,  but  also  because  it  gives  entrance  to  the  disease 
germs  in  the  air  about  us. 

Uses  of  Coagulation.  —  The  blood  has  a  successful 
way  of  stopping  its  flow  from  a  wound,  if  not  too 
large  a  vessel  has  been  severed.  It  is  by  coagulation,  a 
process  described  in  a  former  section,  which  by  plug- 
ging up  the  vessels  prevents  loss  of  blood.  When,  how- 
ever, a  moderately  large  artery  is  cut  or  broken,  the 
force  of  the  current  is  so  strong  that  before  coagula- 
tion can  take  place  so  much  blood  may  be  lost  as  to 
produce  death.  In  such  a  wound  the  blood  vessels 
must  be  compressed  by  force  until  coagulation  can  take 
place.  Of  course,  a  physician  should  have  charge  of 
such  cases  as  soon  as  possible.  But  as  death  might 
result  before  the  physician  could  come,  a  knowledge  of 
what  to  do  is  of  great  importance. 

If  only  capillaries  or  small  vessels  are  cut,  the  bleed- 
ing is  slow,  and  chance  for  a  clot  to  be  formed  is 
good,  so  there  is  not  much  danger.  It  is  when  an 
artery  is  cut  that  there  is  danger.  By  referring  to  Fig. 
26,  the  positions  of  the  main  arteries  may  be  seen. 
Since  the  blood  in  the  arteries  flows  from  the  heart 
toward  the  ends  of  the  extremities,  it  is  plain  that  to 
stop  the  flow  of  the  blood  we  must  press  on  the  artery 
on  the  side  of  the  cut  toward  the  heart.  We  can  push 
down  hard  on  the  artery  with  our  fingers,  or  the  pres- 
sure can  be  made  by  tying  a  bandage  tightly  around 


60  HYGIENE   OF  THE   CIRCULATION 

the  limb  with  a  hard  knot  just  over  the  artery.  Hold- 
ing the  limb  up  above  the  heart  will  help  much.  If 
the  case  is  severe,  the  bandage  may  be  made  tighter 
by  twisting  it  up  with  a  short  stick.  The  knot  may 
be  made  harder  by  including  in  it  a  small,  round  stone 
or  other  hard  body  to  press  down  on  the  artery. 

Care  of  the  Heart. — The  center  of  the  circulatory 
system  is  the  heart.  Moment  by  moment  our  lives 
depend  on  the  correct  and  continuous  action  of  this 
pump  that  works  night  and  day,  it  may  be  through  a 
long  life.  We  have  seen  that  its  action  is  regulated 
through  the  nervous  system  by  the  conditions  of  the 
various  parts  of  the  body.  It  beats  more  quickly  and 
vigorously  when  exercise  makes  necessary  a  more  rapid 
circulation  through  the  muscles,  and  more  slowly  dur- 
ing sleep  when  the  body  is  most  quiet.  During  health 
and  good  general  condition  of  the  body  the  heart  does 
its  work  without  trouble  or  fault,  adapting  itself  to 
violent  exercise  or  the  most  quiet  rest. 

Effects  of  Narcotics.  —  It  is  very  important  then  to 
do  nothing  that  will  disturb  the  nicely  regulated  way 
in  which  the  circulatory  system  works.  As  has  been 
seen,  the  stimuli  which  come  from  the  various  parts  of 
the  body  by  means  of  the  nervous  system  make  the 
heart's  action  and  the  expanding  and  contracting  of 
the  blood  vessels  just  right  for  the  needs  of  the  different 
parts  of  the  body.  If  the  heart  or  blood  vessels  re- 
ceive stimuli  from  artificial  sources,  the  natural  regu- 
lation of  their  action  is  disturbed,  and  the  various  parts 
of  the  body  must  suffer  in  consequence.  The  most 
common  substances  used  by  man  causing  this  disturb- 
ance of  the  circulation  are: 


ALCOHOLIC  DRINKS,   ETC.  6 1 

Alcoholic  Drinks,  Tobacco,  Coffee,  and  Tea.  —  Emi- 
nent physiologists  have  come  to  the  conclusion  that 
alcohol  acts  directly  on  the  heart,  weakening  its  action 
and  decreasing  its  power  of  doing  work.  While  the 
heart  may  beat  faster  through  the  presence  of  alcohol 
in  the  blood,  the  beats  are  not  so  strong,  and  the  whole 
effect  is  to  make  the  blood  circulate  less  rapidly.  Alco- 
hol is  thus  regarded  as  having  a  paralyzing  action  on 
the  heart. 

When  alcohol  is  given  to  a  patient  suffering  from 
some  disease  or  from  an  injury,  the  heart  may  be  stimu- 
lated to  greater  action.  In  such  a  case  the  result,  it  is 
maintained,  is  not  due  to  the  direct  action  of  the  alcohol 
on  the  heart.  But  this  whole  question  would  require 
for  its  discussion  much  technical  knowledge,  and  would 
be  out  of  place  in  this  book.  It  is  here  brought  to 
notice  simply  to  show  that  it  is  a  more  difficult  subject 
than  it  is  considered  by  those  who  are  ready  to  make 
so  many  definite  assertions  regarding  it. 

Whatever  may  be  the  immediate  cause,  however,  it 
is  well  known  that  certain  diseases  of  the  heart  are 
likely  to  follow  the  long-continued  use  of  alcoholic 
drinks.  The  general  vitality  and  tone  of  the  heart  are 
impaired,  and  it  is  thus  rendered  more  liable  to  attack 
by  disease.  Its  structure  may  become  distinctly  modi- 
fied, fatty  and  connective  tissue  taking,  to  some  ex- 
tent, the  place  of  muscular  tissue,  as  seen  in  fatty 
degeneration  of  the  heart.  The  smaller  blood  vessels 
in  certain  regions  of  the  body  may  become  in  a 
measure  paralyzed,  and  thus  permanently  distended. 
It  is  claimed  also  that  alcohol  has  the  power  to  take 
a  part  of  the  oxygen  out  of  the  red  Wood  corpuscles, 


62  HYGIENE    OF   THE   CIRCULATION 

whose  office,  it  will  be  remembered,  is  to  carry 
oxygen. 

Tobacco  used  continuously  in  excess  will  affect  the 
heart  injuriously,  weakening  it  and  making  its  action 
irregular.  It  also  weakens  the  blood  vessels.  Coffee 
and  tea  also  have  an  injurious  effect  when  used  in 
excess. 

Effect  of  Excessive  Exercise.  —  It  has  been  pointed 
out  that  when  the  muscles  of  the  body  are  thrown  into 
exercise,  the  heart  works  harder  to  keep  the  circulation 
in  the  right  condition  for  the  muscles.  Continued  vio- 
lent action,  such  as  running  or  climbing  a  mountain, 
and  the  like,  forces  the  heart  to  do  much  extra  work.  Of 
course,  like  the  other  muscles,  it  can  stand  this  without 
injury  if  not  carried  to  excess,  but  excessive  exercise 
affects  the  heart  as  well  as  the  body  muscles.  Persons 
with  hearts  that  are  naturally  weak  or  that  have  been 
weakened  by  sickness  must  be  careful  to  avoid  sudden 
violent  action  of  the  body.  Violent  actions  on  the  part 
of  young  persons  recovering  from  some  weakening  dis- 
ease may  lead  to  permanent  weakness  of  the  heart,  or 
in  some  cases  may  prove  fatal. 


CHAPTER    VI 

HOW    THE   BODY    WORKS.      ITS    NEED    FOR    FOOD   AND 
OXYGEN 

WE  take  food  so  that  we  may  be  able  to  do  work 
and  to  grow,  also  to  replace  parts  of  the  body  that  are 
worn  away.  We  know  that  if  the  body  receives  no 
food  it  soon  loses  in  weight,  the  person  becomes  faint 
and  weak,  and  after  a  time  the  body  is  unable  to  do 
anything,  the  heart  stops  beating,  and  death  results. 

But  how  does  food  help  us  work  ?  This  is  a  subject 
difficult  to  study;  but  we  may  learn  something  of  it  if 
we  examine  some  of  the  machines  invented  by  man 
and  see  what  conditions  are  necessary  for  them  to  keep 
up  their  action.  First,  then,  let  us  consider  how  the 
body  may  be  regarded  as  a  machine. 

The  Body  as  a  Machine.  — The  study  we  have  been 
giving  to  the  body  shows  it  to  be  a  very  complex 
machine.  Many  kinds  of  work  are  constantly  being 
performed  by  its  different  parts,  such  as  pumping  by 
the  heart,  moving  and  changing  the  food  by  the 
stomach  and  intestines,  seeing  by  the  eye,  hearing  by 
the  ear,  and  so  on. 

Organs  and  Systems.  —  In  physiology,  a  single  part 
that  does  one  kind  of  work  is  called  an  organ.  Thus 
the  eye  is  the  organ  of  sight,  the  ear  is  the  organ  of 
hearing,  and  the  heart  is  one  of  the  organs  of  circula- 
tion. All  the  organs  that  together  perform  one  of 

63 


64  HOW   THE   BODY    WORKS 

the  great  actions  of  the  body  make  up  what  we  call 
a  system.  The  circulatory  system  includes  the  heart 
together  with  the  arteries,  veins,  and  capillaries;  that 
is,  all  the  organs  which  manage  the  blood  and  keep  it 
moving  through  the  body.  Besides,  we  have  the  nerv- 
ous system,  the  muscular  system,  the  bony  system,  and 
the  digestive  system.  In  each  case,  the  system  includes 
all  the  separate  organs  that  do  the  parts  of  the  work  of 
one  big  process.  Now,  as  the  body  as  a  whole  is  com- 
posed of  these  systems  grouped  together,  it  can  be  seen 
what  is  meant  by  saying  it  is  very  complex. 

What  is  meant  by  Organization.  Its  Advantage.— 
That  all  these  parts  work  together  so  well  proves  that 
all  is  well  organized.  What  is  meant  by  "  organized  "? 
This  can  be  illustrated  by  a  school.  The  pupils  in  it 
are  put  into  various  grades  according  to  their  age  and 
advancement  in  their  studies,  then  in  each  grade  are 
arranged  classes  in  the  different  subjects.  The  other 
people  about  the  school  building — the  principal,  the 
teachers,  and  the  janitor  —  also  have  special  things  to 
do.  Then  there  are  programmes  of  study,  recitation, 
and  play.  By  planning  the  school  in  this  way,  a  large 
number  of  pupils  study,  recite,  and  do  the  other  school 
work  without  loss  of  time  and  energy.  Without  plans 
of  this  kind,  all  would  be  confusion,  and  no  work 
could  be  accomplished. 

A  shop  or  store  would  further  illustrate  organiza- 
tion, for  in  it  each  person  employed  does  some  part 
of  the  whole  work  to  be  done.  The  one  who  manages 
the  business  plans  a  great  piece  of  work  which  no  one 
could  do  alone,  but  by  dividing  it  up  into  parts  which 
separate  people  can  do,  the  whole  is  easily  done.  When 


TISSUES  65 

all  that  each  does  is  brought  together,  the  work  of  the 
business  is  complete.  It  is  only  by  organization  that 
great  things  can  be  accomplished.  These  are  examples 
of  organization  of  people  into  systems.  An  example  of 
organization  of  non-living  things  would  be  that  of  a 
steam  engine.  Here  the  parts  are  fitted  together,  so 
that  they  accomplish  their  end,  but  in  an  unorganized 
heap  they  could  do  nothing.  In  nature  it  is  only  in 
animals  and  plants  that  we  see  organization  of  the 
parts  to  accomplish  the  work.  It  is  for  this  reason  that 
living  things  are  called  organisms.  Man  and  the  higher 
animals  are  the  most  complex  organisms.  There  are 
forms  of  animals  much  more  simple  than  man.  They 
do  not  have  so  many  organs  to  do  the  work  of  living, 
and,  consequently,  their  lives  are  more  simple. 

Tissues.  — The  word  "tissue"  is  often  used  in  physi- 
ology, and  as  it  is  a  convenient  and  important  word  we 
should  know  its  meaning.  By  it  is  meant  one  of  the 
materials  of  which  the  parts  of  the  body  are  made. 
Some  examples  of  tissues  are  bony  tissue,  muscular 
tissue,  fatty  tissue,  connective  tissue,  nervous  tissue.  The 
hard  solid  portion  of  a  bone  is  made  of  bony  tissue,  the 
part  of  a  muscle  which  contracts  and  does  the  work  is 
the  muscular  tissue.  The  connective  tissue  includes  the 
tendons,  ligaments,  and  bands  that  tie  bones  together 
into  joints,  fasten  muscles  to  bones,  and  hold  parts  of 
organs  together.  Nervous  tissue  is  the  material  of  the 
brain,  the  spinal  cord,  and  the  nerves. 

The  tissues  are  living,  and  it  is  they  which  must  be 
supplied  with  food  and  oxygen.  The  bony  and  con- 
nective tissues  are  mostly  used  for  support  for  other 
tissues  and  organs,  while  the  nervous  and  muscular 

IND.    PR.    PHYS. 5 


66    .  HOW   THE  BODY    WORKS 

tissues  are  the  great  workers  of  the  body.  Especially 
is  this  true  of  the  muscular  tissue,  as  we  have  seen. 

The  Work  of  the  Body.  — The  main  work  of  the  body 
is  to  produce  motion,  but  there  are  other  important 
things  its  tissues  must  do.  The  body  must  make  heat 
to  keep  itself  warm.  Parts  of  it  must  make  certain  liq- 
uids, such  as  saliva,  gastric  juice,  and  others,  for  diges- 
tion and  other  purposes.  Nervous  impulses  must  be 
formed  to  act  on  the  muscles.  These  are  some  of  the 
things  the  body  must  do.  How  does  the  body  perform 
this  work  ?  Heat  and  motion  are  produced  by  us  out- 
side of  the  body  by  certain  contrivances  for  those  pur- 
poses, and  we  can  best  understand  how  the  body  can 
produce  heat  and  motion  by  comparison  with  our 
invented  machinery. 

The  Work  of  a  Steam  Engine.  —  The  steam  engine  is 
a  very  common  means  of  producing  motion.  The  mo- 
tion is  made  by  burning  coal  in  a  furnace,  which  makes 
great  heat.  This  heats  the  water  until  it  turns  to 
steam;  the  steam  pushes  on  the  piston  and  moves  it. 
The  piston  is  connected  with  the  rest  of  the  machinery 
and  thus  the  work  is  done.  In  this  we  get  both  heat 
and  motion  by  burning  coal.  In  burning  the  coal  we 
must  have  plenty  of  air.  The  air  is  a  mixture  of  sev- 
eral things.  One  of  them  is  the  gas  oxygen.  It  is  the 
oxygen  of  the  air  that  is  used  in  burning  the  coal.  Both 
the  coal  and  the  oxygen  are  necessary  to  produce  the 
heat  and  motion.  If  either  is  lacking,  the  fire  goes 
out  and  the  engine  stops. 

How  the  Body  is  like  an  Engine.  —  To  keep  itself 
warm  and  to  perform  its  varied  motions,  the  human 
body,  like  the  steam  engine,  requires  oxygen,  while 


WHAT  HEAT  DOES  6? 

food  takes  the  place  of  coal.  Indeed,  the  food  we  eat 
contains  some  of  the  same  substances  that  are  in  coal, 
and  if  we  dry  it,  we  can  burn  it  in  the  furnace  of  an 
engine  and  cause  heat  and  motion.  Now  some  other 
things  show  the  body  to  be  acting  like  a  steam  engine* 
If  you  catch  all  the  substances  which  come  out  of  the 
chimney  and  examine  them  carefully,  they  are  found 
to  be  mainly  carbonic  dioxide  and  vapor  of  water,  and 
then  if  you  examine  the  substances  which  the  body 
throws  off  at  the  lungs,  skin,  and  kidneys,  they  also 
are  found  to  consist  mainly  of  carbonic  dioxide  and 
water.  Coal  and  oxygen  are  burned  to  carbonic  dioxide 
and  water  in  the  engine,  while  food  and  oxygen  are 
burned  to  carbonic  dioxide  and  water  in  the  body,  and 
in  both  cases  heat  and  motion  are  produced. 

The  "  burning,"  as  we  have  called  it,  seems  different 
in  the  body  from  that  in  the  engine.  In  the  engine  it 
takes  place  rapidly,  causing  great  light  and  heat,  while 
in  the  body  it  takes  place  more  slowly,  causing  much 
less  heat,  less  motion,  and  no  light.  But  after  all,  the 
union  of  the  food  with  oxygen  is  the  same  as  the  union 
of  coal  with  oxygen.  The  chemical  word  for  "  burn- 
ing," as  used  here,  that  is,  for  the  union  of  oxygen  with 
other  substances,  is  oxidation.  The  substance  burned 
is  said  to  be  oxidized.  Just  as  the  work  of  the  engine 
stops  when  coal  and  oxygen  are  no  longer  supplied,  so 
the  work  of  the  body  stops  when  it  is  deprived  of  food 
and  oxygen. 

What  Heat  Does.  —  If  we  examine  the  work  done  in 
the  world,  it  can  mostly  be  traced  to  the  agency  of 
heat. 

Heat  gives  rise  to  the  currents  of  air  or  winds  which 


68  HOW   THE   BODY    WORKS 

sail  our  ships  or  turn  our  windmills  or  form  the  waves 
that  beat  against  the  shores,  breaking  them  down  and 
grinding  them  up. 

Heat  evaporates  the  water  from  the  ocean,  which, 
after  being  carried  by  the  winds,  falls  on  the  land,  to 
run  back  again,  in  its  course  carving  out  mountains 
and  hills  and  building  up  new  land,  as  well  as  carry- 
ing loads  for  us,  or  running  our  machinery. 

Heat  from  oxidations  runs  the  many  forms  of  en- 
gines now  employed  to  do  a  great  amount  of  the  work 
that  is  accomplished  by  civilized  nations. 

Heat  also  does  the  work  of  our  bodies  by  means  of 
oxidations  of  food  and  air. 

Food  needed  for  Growth  and  Repair.  —  In  one  very 
important  way,  however,  the  body  is  not  like  the 
engine.  An  engine  can  not  repair  its  own  parts,  and 
the  fuel  supplied  to  it  has  nothing  to  do  with  building 
up  its  own  material.  The  body,  however,  not  only 
keeps  warm  and  does  work,  but  it  grows  and  repairs 
Us  own  parts,  and  the  material  needed  for  this  repair, 
as  well  as  that  burned  up  to  produce  heat,  or  motion, 
or  some  other  form  of  energy,  must  be  supplied  in  the 
food. 

Composition  of  the  Body.  —  Every  tissue  of  the  body 
contains  compounds  of  carbon,  hydrogen,  oxygen,  and 
nitrogen.  These  compounds,  with  water,  make  up  by 
far  the  greatest  part  of  the  body.  Besides  these  sub- 
stances, there  exist  in  many  of  the  tissues  some  others 
which  serve  particular  purposes.  The  most  conspicu- 
ous example  is  that  of  osseous  tissue,  which  contains, 
as  we  have  seen  in  the  study  of  the  bones,  compounds 
of  lime.  In  the  tissues  small  amounts  of  compounds 


WASTES  69 

containing  sulphur,  phosphorus,  iron,  sodium,  potas- 
sium, chlorine,  and  some  other  substances  may  be 
found. 

All  these  substances  must  be  in  the  food  and  drink, 
the  study  of  which  will  be  taken  up  in  the  next  chapter. 
It  may  therefore  be  said  that  one  other  object  of  the 
food  is  to  supply  materials  for  the  growth  and  repair  of 
the  tissues. 

Wastes.  —  This  is  a  term  which  applies  to  the  com- 
pounds which  result  mainly  from  the  oxidations  of  the 
body  during  its  work  and  growth.  They  are  mainly 
carbon  dioxide,  water,  and  a  nitrogenous  substance 
(which  is  formed  and  excreted  by  the  kidneys )  called 
urea.  They  are  called  wastes  because  they  can  no 
longer  be  of  use  to  the  body  and  must  be  thrown  away 


CHAPTER    VII 
FOODS 

The  Forms  of  Food,  as  we  see  them  brought  to  the 
table,  are  mixtures  of  certain  substances,  some  of  which 
occur  in  many  different  foods.  For  example,  sugar  is 
naturally  in  the  fruits,  and  is  often  added  to  other 
foods  in  their  preparation.  Again,  starch  is  present 
in  the  bread,  in  the  potatoes,  in  the  pudding,  and  in  the 
pie.  Fat  or  oil  may  occur  in  several  foods,  either  natu- 
rally, as  in  the  meats,  or  by  its  use  in  cooking. 

Kinds  of  Food  Substances.  —  For  convenience  in 
study  these  foods  are  put  into  groups  which  may  be 
called  the  food  groups.  The  food  substances  —  that  is, 
the  substances  which  make  up  the  foods  that  are  placed 
on  the  table  —  are  of  two  general  classes,  the  organic 
and  the  inorganic. 

The  organic  food  substances  are  those  which  are  de- 
rived from  plants  and  animals,  and  make  up  most  of 
the  food  we  take.  Among  these  substances  those  most 
alike  in  their  composition  are  put  together  into  groups. 

The  Starch  and  Sugar  Group.  —  Chemists  have  found 
that  the  different  kinds  of  starches  and  sugars  are  all 
composed  of  the  same  elements,  and  are  alike  in  many 
other  ways.  Indeed,  starch  can  be  changed  into  sugar. 
Gums,  such  as  gum  arabic,  belong  to  the  same  group. 

The  starches  are  derived  from  plants,  and  are  espe- 
cially abundant  in  all  grains  and  seeds  used  for  food. 

70 


THE    GROUP   OF  PROTEIDS  Jl 

They  occur  also  in  the  leaves,  stems,  and  roots  of  plants, 
as  in  cabbage,  lettuce,  potatoes,  and  sweet  potatoes. 
Sugars  are  usually  obtained  from  plants,  but  one  kind 
is  found  in  milk.  They  are  found  in  ripe  fruits,  and, 
indeed,  may  be  in  any  part  of  the  plant. 

In  the  plant  the  starch  is  often  changed  to  sugar,  as 
is  seen  in  the  change  from  a  green  to  a  ripe  apple.  Man 
has  learned  how  to  accomplish  this  change,  and  every 
year  large  quantities  of  starch  are  made  into  sugar  for 
the  market.  Gums  form  but  an  unimportant  part  of 
the  food. 

The  Group  of  Fats. — This  group  includes  the  vari- 
ous fats  and  oils  found  in  milk,  in  the  flesh  of  animals, 
and  in  plants.  The  words  "fats"  and  "oils"  are  simply 
relative  terms,  fats  being  applied  to  those  of  the  group 
which  are  solid  at  an  ordinary  temperature,  of  which 
tallow  is  an  example,  while  oil  is  a  liquid  at  the  same 
temperature,  such  as  olive  oil. 

The  Group  of  Proteids.  —  A  third  group  of  organic 
food  substances  consists  of  a  number  of  substances 
that  are  very  common  in  the  different  forms  of  food, 
but  since  they  are  not  commonly  separated  from  them, 
as  are  starch,  sugar,  and  fat,  they  are  not  familiar  sub- 
stances. The  most  familiar  example  of  this  group  is 
the  white  of  an  egg.  This  is  mainly  egg  albumen,  with 
a  large  amount  of  water. 

Most  of  the  other  members  of  the  group  of  proteids, 
if  they  could  be  separated  from  the  substances  which 
contain  them,  would  look  and  act  very  much  like  the 
albumen  of  the  white  of  an  egg.  For  example,  they 
would  coagulate  when  heated,  and  act  in  other  ways 
which  lead  chemists  to  recognize  them  as  similar. 


72  FOODS 

The  lean  of  meats  is  rich  in  proteids.  There  is  a 
proteid  in  milk. 

Cheese  has  a  large  amount  of  proteid  in  it.  Peas 
and  beans  are  rich  in  proteids,  and  grains  have  a  con- 
siderable amount.  Some  vegetables,  such  as  potatoes, 
have  small  amounts. 

The  proteids  contain  nitrogen  while  the  other  groups 
do  not.  From  this  fact  the  proteids  are  sometimes 
called  nitrogenous  foods,  and  the  fats,  starches,  and 
sugars  are  called  the  non-nitrogenous  foods. 

Some  plants  can  manufacture  all  the  different  kinds 
of  food  substances  from  the  soil,  water,  and  air. 
Animals  can  not  do  this,  but  must  have  the  pro- 
teids, fats,  sugars,  and  starches  already  made  for 
them.  Consequently,  they  must  take  for  food  either 
such  substances  as  a  plant  has  produced,  or  the  tis- 
sues of  some  animal  that  has  eaten  plants  or  other 
animals. 

All  animals  live  by  the  death  of  other  organisms, 
man  being  no  exception.  Many  plants  are  like  ani- 
mals in  this  respect.  Those  which  do  not  possess  the 
green  color  found  in  leaves,  called  chlorophyll,  can  not 
live  on  inorganic  foods.  The  mushrooms,  molds,  mil- 
dews, and  many  forms  of  parasitic  plants  —  that  is, 
plants  that  live  on  the  substance  of  other  plants  —  are 
examples.  All  plants  without  chlorophyll  must  have 
for  their  food  some  organic  substance. 

Food  Substances  ready  to  be  Oxidized. — The  food 
substances  that  we  have  just  been  studying  can  all  be 
burned;  that  is,  they  will  unite  with  oxygen,  either 
within  the  body  or  outside  the  body.  The  fats, 
starches,  and  sugars  when  oxidized  produce  water  and 


THE    USE    OF  INORGANIC  FOODS  73 

carbon  dioxide  as  well  as  heat.  The  proteids,  in  addi- 
tion, give  off  a  substance  containing  nitrogen. 

We  could  burn  meat,  bread,  eggs,  peas,  beans,  and 
the  various  grains  in  the  furnace  of  a  boiler  and  get 
sufficient  heat  to  run  the  engine.  We  have  already 
seen  that  they  are  oxidized  in  the  body  with  the  same 
results. 

The  Inorganic  Foods.  —  This  division  includes  water 
and  various  mineral  substances,  of  which  the  great- 
est amount  used  is  common  salt.  The  others  are  taken 
in  very  small  amounts  mixed  with  the  other  foods. 
The  salts,  or  salines,  are  the  same  as  those  mentioned 
as  being  in  the  tissues  of  the  body.  They  are  com- 
pounds of  lime,  magnesium,  sodium,  and  potassium. 
They  are  absorbed  by  the  plants  from  the  soil,  and 
from  this  source  we  obtain  them,  either  directly  from 
the  plants  or  indirectly  through  the  flesh  of  animals 
which  have  fed  on  them. 

The  Use  of  Inorganic  Foods.  —  From  the  inorganic 
group  of  foods  the  tissues  obtain  their  supplies  of  the 
mineral  substances  used  in  their  structure,  but  none  of 
these  can  be  oxidized,  and  hence  can  not  be  the  source 
of  heat  or  motion. 

Water,  the  principal  one  of  the  inorganic  foods, 
is  also  one  of  the  most  important.  Its  use  is  to 
form  solutions  so  that  the  liquid  blood  and  lymph 
may  be  possible,  and  that  the  tissues  may  make  the 
exchanges  with  the  blood.  All  the  processes  of  the 
body  depend  on  the  presence  of  water.  The  tissues 
might  be  said  to  live  on  substances  dissolved  in  water. 
A  slight  reduction  of  this  water  causes  a  severe  thirst, 
which  drives  us  to  make  good  the  loss. 


74  FOODS 

The  Proportion  of  the  Different  Foods  needed  in  the 
Body.  —  To  accomplish  the  three  main  purposes  of 
foods  —  viz.  to  keep  the  body  warm,  to  furnish  it 
means  to  perform  its  work,  and  to  furnish  it  with  mate- 
rial for  growth  —  it  is  evident  that  there  might  be  a 
combination  of  food  substances  that  would  have  the 
best  proportions. 

What  these  proportions  are  has  been  the  subject  of 
much  investigation.  It  has  been  shown  that  if  too 
much  nitrogenous  food  be  taken,  the  labor  of  the  body 
is  greatly  increased  in  getting  rid  of  the  extra  amount. 
If  this  is  continued  for  a  considerable  length  of  time, 
serious  diseases  are  sure  to  follow. 

The  right  proportion  of  the  non-nitrogenous  foods  to 
the  nitrogenous  is  said  to  be  about  four  parts  of  the 
first  to  one  of  the  second.  These  proportions  are  about 
those  in  milk,  or  in  wheat  flour  when  in  the  form  of 
"  Graham  flour." 

Meats,  peas,  and  beans,  when  taken  alone,  have 
more  than  the  needed  nitrogen,  while  rice  and  pota- 
toes do  not  have  enough. 

Many  experiments  have  been  made  to  determine  just 
how  much  of  each  kind  of  food  is  sufficient  for  the  body. 
Such  knowledge  is  of  great  practical  •  value  when  food 
must  be  provided  for  large  numbers,  such  as  armies, 
navies,  and  large  bodies  of  working  men,  to  determine 
how  much  of  each  kind  to  buy  and  how  much  to  dis- 
tribute to  each  man.  If  the  same  rules  were  applied 
to  the  selection  of  food  for  family  life,  no  doubt  very 
much  could  be  saved  that  is  now  worse  than  wasted. 
As  the  food  is  brought  to  the  table  of  the  ordinary 
family,  all  the  groups  are  pretty  sure  to  be  sufficiently 


THE    USE   AND   ABUSE    OF   THE  APPETITE       75 

represented,  so  that  each  one  is  supplied  with  both  sub- 
stances that  contain  nitrogen  and  those  that  do  not; 
but  people  who  are  very  poor  are  not  always  able  to 
procure  food  in  enough  variety  to  afford  the  proper 
nourishment. 

The  Use  and  Abuse  of  the  Appetite.  —  It  is  important 
to  remember  that  the  use  of  the  appetite,  or  desire  for 
food,  is  to  regulate  the  amount  and  kind  of  food  neces- 
sary for  the  body.  Just  as  the  body  has  a  way  of  in- 
creasing or  diminishing  the  respiration  according  to  its 
needs,  and  a  way  of  regulating  the  beating  of  the  heart 
for  different  conditions,  so  by  means  of  hunger  and 
thirst  it  can  regulate  the  amount  of  food  and  drink 
necessary  for  its  growth.  As  the  needs  of  the  body 
vary  much  according  to  age,  occupation,  climate,  and 
the  particular  disposition  of  the  individual,  it  would  be 
impossible  to  determine  for  each  one  on  every  day  just 
the  amount  and  kind  of  food  he  needs.  If  the  wisest 
scientific  men  were  wise  enough  to  do  this,  it  would 
still  be  impossible  for  the  great  majority  of  people  to 
make  use  of  this  wisdom  from  hour  to  hour.  Thus 
we  see  the  great  importance  of  appetite  and  of  having 
it  work  naturally.  If  this  one  of  nature's  most  impor- 
tant gifts  is  disturbed  or  becomes  unnatural,  the  body 
may  take  in  too  much  food  or  too  little,  or  the  food 
may  be  of  the  wrong  kind,  lacking  some  of  the  elements, 
and  having  too  much  of  others,  which  in  time  is  sure 
to  lead  to  very  serious  results.  The  appetite  may  be 
disturbed  or  become  unnatural  either  by  sickness  or  by 
forming  habits  of  eating  or  drinking  too  much  food  or 
food  of  the  wrong  kind.  In  case  of  sickness  a  physi- 
cian should  be  consulted  as  to  the  proper  diet.  Where 


76  FOODS 

poverty  and  want  do  not  exist,  the  tendency  seems  to 
be  to  get  into  habits  of  eating  too  much.  Parents 
often  urge  upon  little  children  more  food  than  they 
need.  Habits  of  eating  are  thus  formed  with  an  appe- 
tite not  quite  natural.  Craving  for  food  then  grows 
beyond  the  needs  of  the  activity  of  the  body.  When 
more  food  is  taken  into  the  blood  than  is  needed,  the 
body  is  overworked  in  trying  to  rid  itself  of  the  excess, 
and  this  constant  overwork  is  sure  in  time  to  bring  on 
severe  troubles,  like  rheumatism,  gout,  kidney  troubles, 
etc.,  besides  rendering  the  body  less  efficient  for  all  its 
work.  A  simple  and  moderate  diet  taken  regularly  is 
of  the  greatest  importance  for  maintaining  health  and 
insuring  a  long  life. 


CHAPTER    VIII 

PARTS  OF  THE  DIGESTIVE  SYSTEM.   CARE  OF  THE 
TEETH 

As  we  learned  in  the  last  chapter,  the  tissues  con- 
stantly require  food  for  their  activity.  But  they  can  not 
use  this  food  until  it  is  much  changed.  As  has  been 
pointed  out,  the  tissues  are  nourished  by  the  blood, 
which  is  carried  to  them  by  the  blood  vessels.  The 
blood  gets  its  supply  from  the  food  we  eat,  but  the 
latter  undergoes  much  change  before  it  enters  the  blood. 

Much  of  the  food  is  solid  material  that  will  not  dis- 
solve in  water,  while  the  plasma  of  the  blood,  that  is 
all  the  blood  except  the  corpuscles,  is  a  liquid.  It  is 
the  plasma  which  gives  food  to  the  tissues. 

Now  it  is  the  work  of  digestion  to  change  the  foods 
so  that  they  can  pass  through  the  lining  membrane  of 
the  alimentary  canal  and  the  walls  of  the  capillary 
blood  vessels  and  into  the  plasma  of  the  blood.  All 
this  is  possible  only  when  the  food  is  in  a  liquid  form. 
Whether  the  food  be  beans,  meat,  bread,  or  potatoes, 
that  part  which  is  to  be  food  for  the  tissues  must  be 
dissolved.  It  is  the  object  of  digestion  to  reduce  food 
to  a  liquid  form. 

Foods  that  require  Digestion.  — The  sugar  is  readily 
soluble  in  water  and  is  usually  already  dissolved  in  the 
food  or  drink  that  we  take ;  consequently,  it  needs  no 
further  action  that  it  may  be  absorbed  into  the  body. 

77 


78  PARTS   OF   THE  DIGESTIVE   SYSTEM 

But  of  the  starches  or  the  proteids  taken  as  foods  some 
can  not  dissolve  sufficiently  in  water  for  this  purpose, 
others  not  at  all. 

The  oils,  it  is  true,  are  in  a  liquid  form,  and  the  fats 
will  be  melted  to  a  liquid  form  by  the  heat  of  the  body, 
but  still  they  will  not  soak  through  the  membranes 
without  special  preparation. 

The  water  remains  unchanged,  being  absorbed  as 
water,  passing  to  all  parts  of  the  body,  and  being 
thrown  out  of  the  body  as  water. 

The  mineral  substances  taken  in  the  food  are  in 
minute  quantities  already  dissolved,  and,  of  course, 
need  no  digestive  action. 

It  may  be  said,  then,  that  of  the  foods,  the  proteids, 
the  fats  and  oils,  and  the  starches  and  the  gums  must 
be  digested. 

How  is  Digestion  Accomplished?  —  The  foods  are 
digested  by  being  taken  into  the  alimentary  canal, 
where  at  various  parts  they  have  mixed  with  them 
certain  liquids  which  will  change  the  food  substances 
so  that  they  become  liquids;  then  the  food  substances 
in  liquid  form  are  absorbed  and  brought  into  the  blood. 

The  Alimentary  Canal.  — The  alimentary  canal  is  a 
tube  about  thirty  feet  in  length,  passing  through  the 
body,  into  which  the  food  is  placed  to  be  subjected  to 
the  liquids  which  make  these  changes  in  the  foods. 
It  is  variously  modified  along  its  course  into  different 
parts  which  perform  different  actions. 

All  these  parts,  together  with  the  organs  connected 
with  them  which  form  the  digestive  liquids,  are  called 
the  digestive  system.  The  digestive  system  consists  of 
the  mouth  and  the  salivary  glands,  the  pharynx,  the 


THE  MOUTH  79 

esophagus,  the  stomach,  the  small  intestine,  with  the 
liver  and  the  pancreas,  and  the  large  intestine. 

Glands.  — The  essential  part  of  digestion  is  accom- 
plished by  liquids  poured  upon  the  foods.  These 
liquids  are  formed  by  organs  called  glands.  Glands 
are  used  also  in  other  parts  of  the  body  to  form  liquids, 
as,  for  example,  to  form  sweat  and  tears. 

Very  simple  forms  of  glands  are  very  minute  tubes 
or  sacs,  which  are  surrounded  by  a  network  of  cap- 
illaries. The  lining  of  a  gland  forms  the  liquid  pecul- 
iar to  it,  which  is  called  its  secretion.  This  flows  out 
of  the  mouth  of  the  tube.  The  gland  tissue  gets  from 
the  blood  near  it  the  material  from  which  it  forms  its 
secretion. 

In  large  glands,  the  tubes  are  divided  into  very 
many  branches,  so  that  the  gland  is  in  the  form  of  a 
tree  with  its  branches,  except  that  the  branches  are 
crowded  and  folded  together  in  a  somewhat  solid 
form. 

The  divisions  of  the  parts  of  the  tubes  greatly  in- 
crease the  secreting  surface  of  the  gland.  In  all  the 
branching  a  network  of  capillaries  follows  each  minute 
branch. 

The  Mouth.  — This  part  of  the  system  can  be  so  well 
studied  from  a  view  of  the  object  itself  that  the  printed 
description  should  be  relied  upon  only  for  learning  the 
names  of  the  parts. 

The  mouth  forms  a  cavity,  which,  when  closed,  is 
well  filled  by  the  tongue  and  the  teeth  projecting  into 
it.  It  has  very  movable  walls  at  the  front  and  sides  in 
the  lips  and  cheeks,  whose  middle  layers  contain  many 
muscles,  which  produce  their  great  number  of  motions. 


80  PARTS   OF  THE  DIGESTIVE   SYSTEM 

The  tongue,  projecting  from  the  floor  of  the  mouth, 
is  extremely  movable.  The  roof,  the  palate,  is  hard 
in  front  and  soft  at  the  back,  ending  in  a  curtain 
which  hangs  down  to  make  the  posterior  wall  of  the 
mouth.  The  two  curved  rows  of  teeth  just  strike  each 
other. 

Besides  the  motions  of  the  lips,  cheeks,  and  tongue, 
the  whole  lower  part  of  the  mouth  can  be  moved  up 
and  down,  from  side  to  side,  and  from  front  to  back, 
by  the  muscles  that  move  the  lower  jaw. 

Determine  from  your  own  mouth  what  these  motions 
are  and  where  the  muscles  are  placed  that  produce  them. 

Placed  in  the  surface 
of  the  tongue  are  the 
little  organs  of  taste. 
In  the  walls  of  the 
mouth  everywhere  are 
little  glands  which  se- 
crete mucus,  the  liquid 
which,  mixed  with  the 
secretion  of  the  salivary 
ig'  '  glands,  is  the  one  which 

LOWER  JAW  BONE  WITH  THE  TEETH.  ,  , 

we  know  as  constantly 

in  the  mouth.    The  salivary  glands  empty  their  secre- 
tion into  the  mouth. 

The  Teeth.  —  The  position  and  characteristic  forms 
of  the  teeth  can  be  plainly  made  out  in  one's  own 
mouth  by  the  use  of  a  mirror.  Fig.  31  shows  how 
the  teeth  in  the  lower  jaw  are  set  into  the  bone.  The 
teeth  appear  in  two  sets.  There  are  ten  in  each  jaw 
of  the  first  set,  which  appears  in  childhood,  and  six- 
teen in  each  jaw  of  the  adult.  The  four  front  teeth 


MASTICA  TION 


81 


in  each  jaw  are  called  incisors ;  the  next  one  on  each 
side  is  a  canine;  the  next  two,  the  bicuspids  or  pre- 
molars ;  and  the  last  three  are  the  molars.  The  same 
teeth  occur  in  many  animals  and  in  the  same  order, 
but  not  always  of  the  same  number.  They  are  much 
varied  in  form  among  the  different  animals  to  adapt 
them  to  the  many  uses  to  be  made  of  them.  Many 
animals  use  their  teeth  for  other  purposes  besides  that 
of  chewing. 

Structure  of  a  Tooth.  —  Fig.  32  shows  the  inter- 
nal view  of  a  tooth  cut  through  from  the  top  or  crown 
to  the  tips  of  the  roots.  It 
shows  it  to  consist  of  three 
substances:  a  layer  of  enamel 
(i)  over  the  crown;  a  layer  of 
cement,  which  is  of  the  same 
structure  as  bone,  around  the 
roots;  these  lie  on  the  main 
substance  of  the  tooth,  the 
dentine,  or  ivory  (2). 

These  are  very  hard  sub- 
stances, the  enamel  being  the 
hardest.  In  the  center  of  the 
tooth  the  hollow  space  is  filled 
with  blood  vessels,  nerves,  and  connective  tissue.  They 
come  in  at  the  points  of -the  roots.  These  together 
are  called  the  pulp  (3). 

Mastication.  —  The  mouth  has  other  uses  besides  its 
action  on  the  foods,  the  chief  one  of  which  is  that  of 
speaking.  Its  work  with  the  foods  is  to  crush  and 
divide  them,  that  they  may  be  swallowed  first,  and 
afterward  may  be  moved  along  the  remainder  of  the 

IND.  PR.  PHYS.  —  6 


Fig.  32. 

STRUCTURE  OF  A  TOOTH. 
i,  enamel;  2,  dentine;  3,  pulp  cavity. 


82  PARTS   OF   THE  DIGESTIVE   SYSTEM 

alimentary  canal  to  be  acted  upon  by  the  digestive 
liquids.  The  process  is  known  as  mastication. 

If  one  will  take  a  portion  of  food  into  his  mouth  and 
proceed  to  masticate  it,  and  at  the  same  time  note  the 
action  of  the"  tongue,  lips,  cheeks,  lower  jaw,  and  teeth, 
he  will  learn  how  deftly  the  food  is  handled  by  them, 
being  first  taken  to  one  part  of  the  mouth,  then  to  an- 
other. All  the  hard  portions  are  brought  between  the 
teeth,  where  they  are  crushed.  In  the  meantime  the 
food  is  mixed  with  saliva  until  it  is  formed  into  a  ball, 
when  it  is,  by  a  quick  motion  of  the  tongue  against 
the  roof  of  the  mouth,  shot  into  the  next  division  of 
the  alimentary  canal,  the  pharynx. 

The  Saliva.  —  The  saliva  has  very  important  func- 
tions. It  allows  dry  food  to  be  swallowed;  it  dis- 
solves the  food  so  that  it  may  be  tasted ;  together  with 
the  mucus  it  moistens  the  lining  of  the  mouth  and  tjie 
larynx,  thus  making  possible  the  motions  of  speech. 

It  has  also  the  power  to  digest  the  starch.  It  does 
this  by  changing  it  into  sugar.  The  food  is  in  the 
mouth  so  short  a  time  that  this  action  is  only  begun 
there,  but  it  is  continued  for  a  time  in  the  stomach. 
The  starch  is  also  digested  in  another  place,  as  we 
shall  see. 

The  Salivary  Glands.  —  The  salivary  glands  are  ar- 
ranged in  three  pairs,  one  pair  in  the  sides  of  the  face, 
just  in  front  of  the  ears,  one  pair  by  the  angles  of  the 
lower  jaw,  and  one  pair  just  under  the  tongue  where 
it  is  attached  to  the  floor  of  the  mouth. 


CARE    OF   THE    TEETH  83 

CARE  OF  THE  TEETH 

The  second  set  of  teeth,  the  permanent  set,  after  it 
is  complete,  must  last  us  the  rest  of  our  lives.  If  one 
is  taken  out,  it  is  not  replaced,  or  if  a  piece  is  broken  off, 
it  does  not  grow  again,  as  a  piece  of  skin  might  do. 
If  a  part  of  a  tooth  decays,  leaving  a  hole  in  it,  it  never 
heals,  but  on  the  contrary  the  hole  gets  larger  and 
larger  until  the  whole  tooth  is  destroyed.  Since  this 
is  true,  it  behooves  us  to  take  good  care  of  these  useful 
tools  which  are  to  serve  us  daily,  it  may  be  for  fifty  or 
sixty  years  or  even  a  longer  time  in  a  long  life. 

Nature's  method  of  protecting  the  human  teeth  is 
by  the  enamel  covering  of  the  crown.  This  hard,  im- 
pervious covering  not  only  gives  a  flinty  surface  for 
cutting  and  grinding  which  stands  the  daily  wear  of 
so  many  years,  but  it  successfully  keeps  out  the  bac- 
teria which  cause  decay  of  the  dentine  if  they  can 
get  at  it.  Thus  we  see  the  importance  of  prevent- 
ing any  break  in  the  enamel,  which  is  often  chipped 
off  by  cracking  nuts  or  biting  hard  surfaces  with  the 
teeth.  Particles  of  food  left  on  the  teeth  for  long 
periods  will  make  places  where  colonies  of  bacteria 
may  form,  resulting  in  the  deposit  of  substances  on 
the  teeth  which  may  even  cause  the  decay  of  the 
enamel,  and  in  course  of  time  of  the  dentine  as  well. 

This  may  especially  occur  near  where  the  tooth 
joins  the  gums,  where  the  enamel  is  the  thinnest  and 
where  food  particles  find  the  easiest  place  to  lodge. 
It  is  plain  that  the  best  thing  to  be  done  is  to  keep 
the  surface  of  the  enamel  clean.  This  is  done,  of  course, 
by  rinsing  the  mouth  after  eating,  by  cleaning  with  a 


84  CARE   OF   THE    TEETH 

cloth,  toothbrush,  toothpicks,  and,  for  particles  be- 
tween the  teeth,  a  thread.  It  is  better  that  the  brush 
be  soft,  so  as  not  to  wound  the  gums,  and  that  the  tooth- 
picks be  of  soft  material,  not  metal,  so  as  not  to  en- 
danger the  enamel.  Although  it  is  not  easily  scratched, 
yet  years  of  bad  usage  could  affect  it.  The  cleansing 
should,  when  possible,  occur  after  each  meal,  but 
surely  after  the  evening  meal,  since  so  long  a  time 
intervenes  between  it  and  the  next  meal. 

The  teeth  of  some  people  are  much  more  ready  to 
decay  than  those  of  others,  and  consequently  more 
care  must  be  taken  by  tjiem  to  avoid  trouble.  But 
with  the  greatest  care  decayed  places  will  appear 
sometimes.  These  begin  as  very  small  places  and  may 
remain  unnoticed  unless  a  special  search  is  made  for 
them.  They  may  even  grow  to  considerable  size  in 
the  mouth  of  a  careless  person.  Now  the  dentist 
knows  how  to  stop  the  decay  of  a  tooth.  He  fills  it 
with  hard  material  which  preserves  it  and  makes  it  still 
a  useful  tooth.  But  the  sooner  the  dentist  discovers 
the  defect,  the  better  it  can  be  treated,  the  more  of  the 
tooth  saved,  to  say  nothing  of  the  pain,  trouble,  and  ex- 
pense escaped.  It  would  be  best  then  for  a  dentist  to 
examine  the  teeth  occasionally  to  see  if  any  trouble  has 
begun.  Once  a  year  is  not  too  often,  and  if  the  teeth 
show  a  disposition  to  have  coats  of  tartar  form  on  them 
the  dentist  should  be  employed  to  clean  them. 

Sometimes  the  permanent  set  comes  in  before  the 
jaw  bones  have  grown  large  enough  to  receive  them 
in  even  rows  and  the  teeth  become  crowded,  and  in 
some  people  these  bones  never  are  large  enough  to 
hold  the  teeth  properly.  In  such  a  case,  if  it  is  thought 


CARE    OF   THE    TEETH  85 

desirable  to  apply  any  remedy,  a  dentist  should  be 
consulted  early,  and  he  may  help  in  the  matter  and 
the  rows  of  teeth  may  be  kept  straight  and  even. 

The  teeth,  like  other  parts  of  the  body,  may  suffer 
from  general  ill  health  or  from  disease  of  the  body. 
In  such  a  case  the  remedy  must  go  further  than  simple 
care  of  the  teeth.  A  physician  is  our  help  in  such  a 
case,  as  the  bad  teeth  are  only  a  sign  of  other  troubles 
in  the  body. 


CHAPTER    IX 


DIGESTION.     CARE   OF  THE   DIGESTIVE   ORGANS 


The  Pharynx.  —  Just  beyond 
tary  tube  becomes  the  pharynx. 


LI  - 


Fig.  33. 

GENERAL  VIEW  OF  THE  ALIMENTARY  CANAL. 

O,  esophagus;  S,  stomach;  SI,  small  intes- 
tine; LI,  large  intestine;  Sp,  spleen;  Z.,  liver 
(raised  up);  G,  gall  bladder;  Pa,  pancreas. 

86 


the  mouth  the  alimen- 
There  are  several  open- 
ings into  this  portion, 
—  one  from  the  mouth, 
one  from  each  nostril, 
one  from  each  middle 
ear,  one  into  the  lar- 
ynx, the  organ  where 
the  voice  is  produced, 
and  the  opening  into 
the  next  division  of 
the  alimentary  canal, 
the  esophagus. 

The  Esophagus.  - 
This  is  the  portion 
of  the  alimentary 
canal  which  extends 
from  the  pharynx  to 
the  stomach.  It  is 
eight  or  nine  inches 
in  length.  It  and  the 
pharynx  are  lined 
internally  with  a 
mucous  membrane. 
Outside  of  this  are 
the  muscular  walls. 


THE   STOMACH 


Swallowing.  — The  food  is  sent  forcibly  from  the 
mouth  into  the  pharynx.  The  pharynx  acts  some- 
thing like  a  funnel  over  the  top  of  the  esophagus. 
When  the  food  is  in  the  pharynx,  its  muscular  walls 
close  around  it  and  quickly  push  it  into  the  esophagus, 
where  portions  of  the  circular  bands  of  muscles  relax 
before  the  food,  and  others  contract  behind  it  to  push 
it  on  into  the  stomach.  Water  is  served  exactly  in  the 
same  way,  and  both  water  and  food  can  be  swallowed 
when  the  head  is  down  as  well  as  when  it  is  erect. 

The  Stomach.  —  This  organ  is  a  part  of  the  ali- 
mentary canal  more  dilated  than  the  other  portions, 
and  so  arranged 

as  to  retain  the  ^|^  Esophagus 

food  in  it  a  cer- 
tain length  of 
time.  (Fig.  34.) 

It  is  in  the 
upper  part  of 
the  abdominal 
cavity  some- 
what to  the  left 
side.  The  open- 
ing at  the  point 
where  the  esoph- 
agus joins  it  is 
called  the  car- 
diac opening;  the  one  at  the  opposite  end,  where  the 
small  intestine  joins  it,  is  called  the  pylorus. 

In  this  latter  place  the  muscular  walls  form  a  ring, 
which  remains  contracted  some  time  after  a  meal  is 
taken,  opening  and  closing  from  time  to  time  to  allow 


Fig.  34. 

SECTION  OF  THE  STOMACH. 


88  DIGESTION 

liquids  to  pass,  thus  retaining  the  more  solid  portions 
for  the  digestion  which  takes  place  in  the  stomach. 
It  finally  relaxes  and  allows  all  the  contents  to  pass 
on  to  the  small  intestine. 

Digestion  in  the  Stomach.  —  The  mucous  coat  of  the 
stomach  is  filled  with  small  glands  which  secrete  a 
liquid  known  as  gastric  juice.  During  the  presence  of 
food  in  the  stomach  this  liquid  is  poured  out  on  it  in 
considerable  quantities. 

Gastric  juice  affects  only  one  of  the  food  groups,  the 
proteids.  When  these  food  substances  are  kept  with 
gastric  juice  a  certain  length  of  time,  they  are  changed 
into  soluble  forms  of  proteids  called  peptones.  This 
change  takes  place  slowly.  To  cause  the  gastric  juice 
to  become  thoroughly  mixed  with  the  food,  the  muscu- 
lar walls  of  the  stomach,  by  contracting  in  many  differ- 
ent directions,  push  it  around,  backward  and  forward, 
many  times. 

Absorption  from  the  Stomach.  —  A  very  great  num- 
ber of  capillary  blood  vessels  forms  a  close  network 
in  the  mucous  coat  immediately  next  to  its  surface. 
This  arrangement  brings  the  blood  so  near  the  liquid 
in  the  stomach  that  nothing  but  a  very  thin  wall  of 
membrane  lies  between  them.  This  allows  the  liquid 
contents  of  the  stomach  and  what  may  be  dissolved 
in  it  to  soak  through  to  the  blood. 

Besides  these  blood  vessels,  there  are  also  the  lym- 
phatics, arranged  in  the  same  position,  so  that  they 
may  also  receive  liquids  from  the  stomach. 

The  process  by  which  a  liquid  may  pass  into  either 
of  these  vessels  is  called  absorption.  The  rapidity  with 
which  it  occurs  is  shown  by  the  quick  effect  which  some 


THE   SMALL   INTESTINE 


89 


medicines   have   on   the   body   when    taken   into   the 
stomach. 

The  Small  Intestine.  — The  small  intestine  is  a  much 
narrower  tube  than  the  stomach.  It  is  about  twenty 
feet  in  length.  It  is  suspended  from  the  margin  of  a 
membrane  called  the  mesentery,  the  inner  edge  of  which 


Fig.  35. 


DIAGRAMMATIC. 


SECTION    OF   THE    Mucous    COAT  OF  THE   SMALL   INTESTINE. 
GREATLY  MAGNIFIED. 

Some  of  the  villi  have  their  covering  layer  removed  to  show  the  structure.     The 
tubes  are  intestinal  glands. 

is  gathered  together  in  one  place  and  fastened  to  the 
back  of  the  abdominal  cavity. 

The  coats  of  the  small  intestine  are  exactly  the 
same  in  name  and  arrangement  as  those  of  the  stom- 
ach. But  the  mucous  coat  differs  from  the  same  coat 
of  the  stomach  in  being  densely  covered  with  minute 
projections. 


90  DIGESTION 

These  are  shown  very  much  enlarged  in  Fig.  35. 
They  are  the  mill.  They  are  special  arrangements 
for  absorption.  Each  one  has  in  it,  as  shown  in  the 
figure,  a  network  of  capillary  blood  vessels,  and  an- 
other kind  of  small  vessels  called  the  lacteals.  They 
empty  into  the  thoracic  duct.  Over  each  villus  is  a 
very  thin  layer  of  tissue,  which  allows  digested  food 
substances  to  pass  through  either  to  the  blood  vessels 
or  the  lacteals,  from  which  it  soon  enters  the  general 
circulation. 

Secretions  coming  into  the  Small  Intestine.  —  The 
mucous  coat  has  in  it  besides  the  villi  a  very  great 
number  of  glands  which  secrete  the  intestinal  juice. 

The  pancreas  is  a  large  gland  lying  just  behind  the 
stomach.  It  forms  the  pancreatic  juice ,  and  pours  it 
into  the  small  intestine  by  its  duct,  which  empties 
into  the  small  intestine  a  short  distance  below  the 
pylorus. 

The  Liver.  —  The  liver  is  a  very  large  gland,  placed 
just  under  the  diaphragm,  mainly  on  the  right  side. 
It  empties  its  secretion,  the  bile,  into  the  small  intes- 
tine at  a  point  very  near  the  opening  of  the  pancreatic 
duct.  The  pancreatic  juice  and  bile  are  immediately 
mixed  with  each  other  and  with  the  food. 

Digestion  in  the  Small  Intestine.  —  The  digestion 
which  goes  on  in  the  small  intestine  may  be  considered 
as  the  most  important  of  all,  since  the  pancreatic  juice 
acts  with  energy  on  proteids  to  change  them  into  the 
soluble  peptones,  on  the  starches  to  change  them  into 
sugar,  and  on  the  fats  to  change  them  into  a  state  in 
which  their  particles  are  extremely  minute,  small 
enough  to  find  their  way  through  the  thin  layer  over 


THE  BILE 


the  villi.     Some  of  the  fats  are  also  changed  into  sub- 
stances which  will  dissolve. 

The  Bile.  — This  liquid  comes  in  very  large  amounts 
into  the  intestine  during  digestion. 

It  has  been  shown  to  have  very  slight  direct  diges- 
tive action  on  any  of  the  foods,  but  it  is  known  to  aid 
the  process  of  digestion 
in  various  ways.  Among 
them  it  may  be  men- 
tioned that  the  bile  makes 
the  contents  of  the  intes- 
tine alkaline,  which  is 
necessary  to  the  action 
of  the  pancreatic  juice, 
and  that  it  in  some  way 
aids  in  the  absorption  of 
the  fats. 

It  has  probably  many 
other  uses,  as  it  is  a  very 
complex  liquid.  Our  or- 
dinary foods  contain  a 
considerable  amount  of 
substances  which  are  not 
acted  on  by  any  of  these 
fluids,  termed  indigest- 
ible parts. 

These  are,  by  the  constant  motions  of  the  small  in- 
testine, sent  along  to  accumulate  in  the  large  intestine. 
They  move  more  and  more  slowly  as  they  pass  along, 
that  the  last  amount  of  digested  food  may  be  ab- 
sorbed before  these  substances  are  removed  from  the 
body. 


Fig.  36. 

LACTEALS. 

Showing  the  connection  of  the  small  intes- 
tine to  the  thoracic  duct  by  the  lacteals  lying 
in  the  mesentery.  Th,  thoracic  duct. 


Q2  DIGESTION 

Absorption.  —  As  already  mentioned,  absorption 
may  take  place  from  the  stomach  and  from  the  small 
and  large  intestines.  It  is  mainly  from  the  small  in- 
testine. The  food,  after  being  absorbed,  may  reach 
the  heart,  and  from  it  the  general  circulation,  by  two 
different  courses: 

i  st.  That  which  is  taken  up  by  the  blood  vessels  goes 
by  the  portal  vein  to  the  liver,  through  the  capil- 
laries of  the  liver  to  the  hepatic  vein  in  the  liver, 
into  the  inferior  vena  cava,  and  thence  to  the 
heart. 

2d.  That  which  is  taken  up  by  the  lacteals  passes  on 
to  the  thoracic  duct,  Fig.  36,  from  which  it  empties 
into  the  left  subclavian  vein,  and  from  this  it  soon 
reaches  the  superior  vena  cava. 
These  two  courses  will  be  made  clear  by  consulting 
the  diagram  of  the  circulation  of  the  blood,  given  in 
the  chapter  on  Circulation. 

Conclusion.  —  In  a  former  section  it  was  said  that 
the  food  of  the  tissues  is  the  blood.  We  have  now 
seen  one  source  from  which  the  food  is  constantly  added 
to  the  blood.  It  is  placed  in  parts  of  a  vessel,  the  ali- 
mentary canal,  and  at  different  places  the  liquids 
change  different  members  of  the  food  groups  into 
solutions.  These  are  given  in  the  following  table: 

1.  Saliva  acts  on  the  Starches. 

2.  Gastric  Juice  acts  on  the  Proteids. 

(  Starches. 

3.  Pancreatic  Juice  acts  on  the  \  Fats. 

[  Proteids. 

These  made  soluble  and  the  sugar  already  dissolved 
bring  all  the  principal  foods  into  liquid  form. 


CARE  OF  THE  DIGESTIVE  ORGANS          93 

THE  CARE  OF  THE  DIGESTIVE  ORGANS 

The  processes  of  digestion  are  all  reflex,  involuntary 
acts,  and  in  good  health  generally  take  care  of  them- 
selves. It  has  been  found  that  the  various  foods  take 
quite  different  lengths  of  time  for  digestion.  It  does 
not  seem  that  a  food  is  better  for  being  quick  to  digest. 
For  those  who  live  on  a  vegetable  diet  do  not  suffer 
inconvenience  from  the  fact  and  are  certainly  as 
healthy  as  a  rule  as  those  who  eat  largely  of  meats, 
although  meats  are  the  more  easily  digested.  The 
human  digestive  system  seems  to  be  adapted  to  the 
digestion  of  foods  that  take  a  long  time  to  digest  as 
well  as  to  those  taking  a  short  time.  The  secretion  of 
the  digestive  juices  and  the  movements  of  the  stomach 
and  intestines  are  accomplished  by  nervous  impulses 
which  under  good  conditions  of  the  body  are  just 
sufficient  to  get  the  best  results  by  reflex  action.  But 
the  normal  working  of  the  nerves  controlling  these 
acts  may  be  disturbed  and  thus  disturb  the  proper 
action  of  the  digestive  system.  Through  this  means 
the  digestive  system  may  be  affected  by  nervous  states 
of  the  body. 

A  fit  of  indigestion  may  be  due  to  excitement  or  mental 
distress.  Dyspepsia  may  be  induced  and  fostered  by 
constantly  thinking  of  the  effect  that  this  or  that  kind  of 
food  has  upon  one.  Of  course  if  some  one  with  delicate 
digestive  organs  learns  by  experience  that  a  certain 
food  disagrees  with  him,  he  ought  to  avoid  it.  But, 
to  say  nothing  of  bad  taste,  it  is  a  bad  habit  from  a 
hygienic  standpoint  constantly  to  question  any  kind 
of  food  presented  and  to  discuss  its  effects. 


94  CARE    OF   THE  ^DIGESTIVE    ORGANS 

We  have  already  spoken  of  the  importance  of  a 
healthy  appetite  in  the  selection  of  food.  It  may  be 
added  that  when  food  is  palatable,  that  is,  "  tastes 
good,"  digestion  generally  proceeds  better.  Thus  there 
is  good  physiological  reason  for  the  proper  prepara- 
tion of  the  food.  And  this  is  the  principal  purpose 
of  cooking.  Cooking,  however,  serves  other  important 
purposes.  It  makes  many  foods  more  digestible,  for 
example,  potatoes,  and  destroys  the  germs  of  many 
diseases  which  may  possibly  be  present.  The  alimen- 
tary canal  is  a  great  gateway  through  which  disease 
may  enter  the  body.  This  subject,  however,  will  be 
more  fully  explained  under  Disease. 


CHAPTER  X 
RESPIRATION 

IT  has  already  been  shown  how  very  necessary 
oxygen  is  to  all  the  tissues  of  the  body.  The  mus- 
cles and  the  brain  especially  use  large  amounts  of 
oxygen  and  they  must  have  a  supply  every  moment. 
The  oxygen,  as  was  explained  in  the  chapter  on  Cir- 
culation, is  mainly  carried  by  the  red  blood  corpuscles 
to  the  tissues.  But  the  blood  gets  its  oxygen  from  the 
lungs,  and  the  lungs  get  their  supply  from  the  air 
breathed  into  them. 

Breathing  has  another  use  besides  bringing  oxygen 
to  the  blood.  It  carries  carbonic  acid  away  from  the 
blood.  It  will  be  remembered  that  when  the  food  of 
the  tissues  unites  with  the  oxygen,  one  of  the  things 
made  is  carbonic  dioxide.  This  is  sometimes  known 
as  a  "  waste  "  substance.  It  must  be  removed.  The 
blood  carries  it  away  from  the  tissues  to  the  lungs, 
and  every  time  the  air  is  breathed  out  from  the  lungs 
some  of  this  carbonic  dioxide  is  thrown  from  the  body. 
Thus  we  see  that  breathing  has  two  very  important 
uses :  one,  the  bringing  of  oxygen  into  the  body,  and  the 
other,  the  taking  of  carbonic  dioxide  out  of  the  body. 

Respiration  is  the  term  for  breathing.  We  shall 
now  study  the  apparatus  for  respiration:  what  its 
parts  are  and  how  they  work  to  draw  the  air  in  and 
throw  it  out  again. 

95 


96 


RESPIRA  TION 


The  Respiratory  Organs.  —  The  part  of  the  appa- 
ratus which  accomplishes  the  constant  removal  of 
the  air  consists  of  the  thorax  and  the  lungs,  which 
hang  as  two  sacs  in  its  cavity,  and  the  tubes  in  the 
lungs,  and  the  large  one  which  connects  them  with 
the  outer  air. 

If  we  name  the  air  passages  in  order  from  without, 
they  are  the  nostrils  and  the  mouth,  the  pharynx,  the 
larynx,  the  trachea,  its  two  large 
branches,  the  bronchi  and  their 
numerous  branches,  the  bronchial 
tubes,  which  become  so  small  in 
their  subdivisions  as  to  require  the 
microscope  to  see  them.  These  end 
in  groups  of  minute  air  sacs,  men- 
tioned above.  They  are  micro- 
scopic. 

A  group  of  these  air  sacs,  or  vesi- 
cles, is  shown  in  Fig.  37.  Among 
these  are  close  networks  of  pul- 
monary capillaries. 
Structure  of  Air  Tubes.  —  The  trachea,  bronchi,  and 
bronchial  tubes  have  a  framework  of  cartilaginous 
rings,  which  hold  them  open  on  all  sides.  The  rings 
have  connective  tissue  between  them  and  around 
them.  The  lining  of  the  passage  is  mucous  membrane, 
in  which  is  a  large  number  of  mucous  glands,  whose 
secretion  is  constantly  forming. 

The  mucus  is  made  to  flow  toward  the  throat  by 
means  of  very  minute  projections,  seen  only  with 
higher  powers  of  the  microscope,  which  are  on  the 
surface  of  the  mucous  membrane.  These  are  the  cilia. 


—  i 
Fig.  37. 

AIR  VESICLES. 


THE   RESPIRATORY  APPARATUS 


97 


They  keep  up  a  constant  waving  motion,  which  car- 
ries the  mucus  along,  together  with  dust  which  settles 
on  it  from  the  air. 

The  Thorax.  —  The  lungs  are  suspended  in  the  cavity 
of  the  thorax.  The  bony  support  of  the  thorax  is 
shown  in  Fig.  38,  and 
consists  of  the  dorsal 
vertebrae,  the  ribs,  and 
the  sternum.  In  this 
framework,  while  the 
ribs  are  attached  at 
their  extremities,  their 
middle  portion  can  be 
moved  up  and  down 
by  muscles  between 
them  and  those  attached 
to  them  from  above  and 
below.  The  muscular 
partition  between  the 
abdomen  and  the  tho- 
rax, the  diaphragm,  forms  the  bottom  of  the  thorax. 

The  Respiratory  Apparatus. — The  essential  part 
of  the  breathing  apparatus  is  a  thin  membrane,  so 
arranged  that  the  oxygen  can  come  on  one  side  and 
the  blood  on  the  other.  In  such  a  case  the  oxygen 
can  pass  into  the  blood  and  the  carbon  dioxide  out. 

In  the  lower  animals,  the  breathing  apparatus  is 
found  in  many  different  forms.  The  gills  of  a  fish 
are  familiar  to  all.  But  all  these  forms,  different  as 
they  may  be  in  other  regards,  have  the  essential 
arrangement  spoken  of  above.  The  oxygen  is  always 
either  in  the  air,  mixed  with  the  other  gases  before 

IND.  PR.  PHYS.  —  7 


Fig.  38. 

BONY  WALLS  OF  THE  THORAX. 


98 


RESPIRA  TION 


mentioned,  or  it  is  dissolved  in  the  water  which  has 
obtained  it  from  the  air. 

In  the  gills  of  the  fish  the  delicate  fringes  are  so 
many  projections  of  very  thin  skin,  through  the  core  of 
which  the  blood  circulates,  but  on  the  outside  of  which 


Larynx. 


Fig.  39. 

THE  HEART  AND  LUNGS. 

the  water  with  the  dissolved  oxygen  is  made  to  pass. 
In  the  lungs  of  a  man  there  are  little  thin-walled  sacs, 
into  the  centers  of  which  the  air  comes,  and  around  the 
surface  of  which  the  blood  circulates.  The  rest  of  the 
apparatus  is  to  pump  the  air  in  and  out  of  the  passages 


INSPIRA  TION 


99 


which  are  connected  with  these  little  air  sacs,  so.  that 
there  may  be  a  constant  change  of  the  air. 

The  Respiratory  Acts.  —  Respiration  consists  of 
two  acts:  inspiration,  by  which  an  amount  of  air  is 
brought  into  the  lungs ;  and  expiration,  by  which 
about  the  same  amount  is  expelled.  The  lungs  hang 
in  the  thorax  as  elastic  sacs  in  air-tight  cavities.  As 
there  is  nothing  but  a  little  liquid  between  the  outer 
walls  of  the  lungs  and  the  walls  of  the  thorax,  the 


Fig.  40. 

THORAX  IN  EXPIRATION. 


Fig.  41. 

THORAX  IN  INSPIRATION. 


pressure  of  the  air,  which  is  fifteen  pounds  to  the 
square  inch,  swells  the  lungs  out  against  these  walls. 

If  now  the  walls  of  the  thorax  are  pulled  away  a 
little  more,  the  pressure  of  the  air  on  the  inside  of 
the  lungs  makes  them  follow  the  retreating  walls  of 
the  thorax.  On  the  other  hand,  when  the  walls  of  the 
thorax  press  upon  the  lungs  they  are  emptied  to  the 
same  extent. 

Inspiration.  —  In  inspiration  the  cavity  is  enlarged. 


1 00  RESPIRA  TION 

This  is  accomplished  in  two  ways:  First,  the  dia- 
phragm being  curved  upward  pulls  itself  down  by 
contraction.  Second,  by  the  contraction  of  one  set 
of  the  muscles  between  the  ribs  (the  external  inter- 
costals )  the  ribs  are  raised,  which  motion,  from  the 
way  they  are  attached  (see  Figs.  40  and  41 ),  throws 
them  out. 

Expiration.  — This  act  consists  in  making  the  cav- 
ity of  the  thorax  smaller.  This  is  done  in  two  ways: 
First,  by  the  muscles  of  the  walls  of  the  abdomen 
contracting  and  pressing  upon  the  contents  of  the 
abdomen,  and  thus  forcing  the  diaphragm  up  again. 
Second,  by  the  other  set  of  intercostals  (the  internal ) 
contracting  to  pull  the  ribs  down.  In  both  acts  many 
other  muscles  may  take  part. 

Nervous  Control.  —  These  motions  are  regulated 
by  nerves,  so  that  one  follows  the  other  in  the  proper 
succession,  frequency,  and  strength,  each  of  which 
varies  much  with  the  varying  activity  of  the  body. 
For,  the  more  work  done,  the  greater  must  be  the 
supply  of  oxygen,  and  the  greater  the  amount  of 
carbon  dioxide  to  be  got  rid  of. 

Although  these  actions  are  involuntary,  yet  the  will 
may  modify  them,  as  it  does  in  the  act  of  speaking. 
Ordinary  respirations  average  about  seventeen  a  minute. 

It  will  be  profitable  to  study  in  oneself  or  another 
how  this  rate  will  vary  in  various  kinds  and  degrees  of 
exercise,  as  well  as  the  character  of  the  act.  Sighing, 
crying,  laughing,  coughing,  sneezing  —  all  are  modifi- 
cations of  the  respiratory  actions,  the  character  of  each 
of  which  the  pupil  should  study  from  the  actions 
themselves. 


HO W  OXYGEN  IS  BROUGHT  TO  THE  AIR  CELLS     IOI 

Changes  in  the  Respiration.  —  When  air  comes  from 
the  lungs  it  has  in  it  an  increased  amount  of  water  and 
carbon  dioxide.  It  also  has  less  oxygen  and  is  warmer. 
Besides  these  changes,  air  from  the  lungs  contains  cer- 
tain organic  substances,  which  are  very  small  in  amount 
and  can  not  be  obtained  in  sufficient  quantity  to  be 
weighed.  They  are  easily  detected  by  the  sense  of 
smell  when  one  passes  from  the  open  air  into  a  poorly 
ventilated  room  in  which  a  number  of  people  are 
gathered. 

From  these  causes,  air  once  breathed  is  not  fit  to 
breathe  again.  There  is  not  enough  oxygen  in  it,  and 
the  organic  substances  it  contains  seem  to  be  real 
poisons. 

Amount  of  Air  Breathed.  —  The  lungs  of  an  adult 
contain  about  one  gallon  of  air.  In  an  ordinary  ex- 
piration only  about  one  pint  of  air  is  thrown ,  out. 
This  can  be  shown  by  breathing  through  a  tube  pass- 
ing under  the  mouth  of  a  bottle  filled  with  water,  and 
inverted  over  water  in  such  a  way  as  to  catch  the  air 
breathed  out. 

The  amount  of  air  breathed  into  the  lungs  is  about 
the  same.  It  can  easily  be  seen  that  a  pint  of  air 
would  only  fill  the  trachea  and  the  upper  air  pas- 
sages. 

How  the  Oxygen  is  brought  to  the  Air  Cells.  - 
Gases  have  the  power  to  pass  freely  into  each  other. 
This  property  is  called  diffusion.  If  a  pint  of  each  of 
a  dozen  gases  were  put  in  different  parts  of  a  closed 
room,  in  a  short  time  they  would  be  equally  distributed 
throughout  the  room. 

By  this  property  the  oxygen  that  is  in   the   upper 


IO2 


RESPIRA  TION 


part  of  the  lungs  diffuses  through  the  rest  of  the  air 
to  the  air  vesicles,  and  the  carbon  dioxide  diffuses 
out  to  the  upper  part,  where  the  acts  of  breathing 
remove  the  old  air  and  bring  in  the  new. 

Changes  in  the  Blood.  —  Once  in  the  air  vesicles, 
the  oxygen  passes  through  the  very  thin  membrane 


Fig.  42. 

LARYNX,  SIDE  VIEW. 

T,  thyroid  cartilage;  C,  cri- 
coid  cartilage;  TV,  trachea; 
H,  hyoid  bone;  E,  epiglottis; 
/,  joint  of  thyroid  cartilage. 


Fig.  43. 

LARYNX,  BACK  VIEW. 

Ar,  arytenoid  cartilages.  The 
other  letters  the  same  as  in  the  pre- 
ceding figure. 


of  their  walls  and  the  walls  of  the  capillaries  into  the 
plasma,  where  it  is  taken  up  by  the  red  corpuscles. 
These,  by  the  current  of  the  blood,  are  carried  to  the 
tissues,  to  which  the  corpuscles  give  up  the  oxygen. 

The  carbon  dioxide,  on  the  other  hand,  passes  from 
the  tissues  to  the  blood,  which  sweeps  it  around  to 
the  lungs,  where  it  escapes.  The  water  is  also  con- 
tinually escaping  at  the  lungs. 


THE  LARYNX 


103 


Thus  the  organs  of  respiration  and  of  circulation 
are  made  the  mediums  of  exchange  between  the  out- 
side air  and  the  tissues  far  removed  from  them. 

The  Voice.  —  Vocal  sounds  are  produced  in  the 
larynx  by  the  air  passing  between  the  parallel  edges 
of  two  folds  of  the  lining  membrane  of  that  organ. 
These  folds  are  the  vocal  cords,  and  are  tightly  stretched 
and  close  together  at  the  time  of  the  sound,  but  are 
relaxed  and  fall  apart  at  other  times. 

The  Larynx. — The  larynx,  Fig.  42,  placed  on  the 
top  of  the  trachea,  consists  of  a  box  formed  of  a  frame 
of  cartilaginous  plates,  some  4 

of  which  can  be  moved  on 
the  others  by  a  number  of 
muscles. 

The  largest  of  these  car- 
tilages, the  thyroid  (see  the 
figure),  forms  the  projec- 
tion in  the  neck  known  as 
11  Adam's  Apple."  It  rests 
on  a  ringlike  base,  the  cricoid 
cartilage. 

The  vocal  cords  are  at- 
tached to  small  cartilages  at  f/g  44 

the  back  Called  the  arytenoid,       LIGAMENTS  OF  THE  VOCAL  CORDS. 

and    tO    the    thyroid    in    front.          ('  and  2),  the  ligaments;    3,  aryte- 

noid  cartilages;    4,  thyroid   cartilage. 

By  the  movements  of  these 

cartilages    the    membranes    of    the    vocal    cords    are 

stretched  and  brought  together,  or  separated. 

The  sound  is  produced  by  the  air  passing  these  in 
a  stretched  condition  and  with  their  edges  close  to- 
gether. Fig.  44  shows  the  ligaments  and  the  cords 


1 04  RESPIRA  TION 

with  the  covering  membrane  removed.  The  sounds 
of  the  letters  are  made  to  differ  from  each  other  by 
giving  different  shapes  to  the  mouth,  pharynx,  and 
larynx. 

The  epiglottis  is  a  lid  which  is  made  to  close  over 
the  larynx  during  swallowing,  for  the  evident  pur- 
pose of  keeping  food  out  of  the  larynx.  It  will  also 
close  promptly  on  breathing  some  poisonous  gases. 
The  larynx,  trachea,  and  lungs  of  some  animal  should 
be  studied.  Also  the  movements  and  forms  of  the 
mouth  in  forming  the  letters. 

No  other  muscles  in  the  body  can  be  moved  with 
the  rapidity  and  precision  of  those  used  in  speaking. 
They  are  greatly  under  the  control  of  the  will,  and 
can  be  trained  to  wonderful  feats  of  singing  and  speak- 
ing, and  ought  to  be  trained  in  every  one  for  reading 
and  talking  well. 


CHAPTER  XI 

PURE  AIR,    BREATHING,   AND   VENTILATION 

GOOD  health  can  not  be  kept  unless  the  body  is 
supplied  at  all  times  with  an  abundance  of  pure  air. 
The  reason  for  this  has  been  repeatedly  stated,  and  the 
importance  of  the  fact  can  not  be  too  strongly  empha- 
sized. At  this  place  we  are  to  consider:  (i)  what  pure 
air  is;  (2)  how  much  each  one  needs;  and  (3)  how  it 
can  be  supplied. 

Pure  Air.  —  What  we  call  pure  air  is  such  as  we  find 
out  of  doors  in  most  places.  It  is  about  the  same  the 
world  over,  because  the  winds  which  blow  first  in  one 
direction  and  then  in  another  keep  it  well  mixed  up 
and  about  the  same  in  its  make-up.  When  man  and 
animals  can  be  supplied  with  this  kind  of  air  for  breath- 
ing they  thrive  well  on  it.  Such  air  is  a  mixture  of 
certain  gases.  It  consists  of  about  one  fifth  oxygen 
and  nearly  four  fifths  nitrogen,  with  small  amounts  of 
carbonic  dioxide  and  vapor  of  water  and  very  small 
amounts  of  other  substances.  Now  if  much  more  than 
the  usual  amount  of  any  of  these  gases  is  present 
or  if  other  gases  are  added,  the  air  is  said  to  be  impure. 
It  is  especially  harmful  for  man  or  animals  if  the  oxygen 
is  diminished  or  the  carbonic  dioxide  is  increased. 

We  have  just  seen  that  in  inspiration  about  a  pint 
of  air  is  taken  into  the  lungs  and  air  passages,  and 

I05 


106     PURE  AIR,   BREATHING,   AND    VENTILATION 

during  the  expiration  that  follows  a  pint  of  air  is 
thrown  out.  The  air  that  is  thrown  out  has  lost 
considerable  of  its  oxygen  and  has  gained  much  car- 
bonic dioxide,  and  besides  it  has  gained  other  impuri- 
ties coming  from  the  body.  It  is  now  quite  impure, 
and  should  not  be  breathed  again.  Indeed,  it  has  so 
much  of  impurity  in  it  that  it  will  spoil  for  breathing 
four  pints  of  good  air.  If  one  is  out  of  doors  when  he 
breathes  out  this  impure  pint  of  air,  the  winds  or  cur- 
rents of  air,  which  are  always  in  motion,  carry  it  away 
and  bring  for  the  next  breath  a  fresh  pint  of  pure  air, 
and  thus  one  is  constantly  supplied  with  an  abundance 
of  the  right  kind  of  air.  But  if  the  body  is  confined 
in  a  closed  room,  the  breathed-out  air  remains  in  the 
room.  If  the  room  is  large,  the  small  amount  of  air 
thrown  out  for  a  short  time,  mixed  with  the  large 
amount  in  the  room,  does  not  make  much  change.  But 
if  the  room  is  small,  or  if  a  large  room  is  occupied  for  a 
long  time  without  change  of  air,  the  many  pints  of  im- 
pure air  breathed  out  will  make  the  whole  roomful 
impure.  That  is,  the  air  in  it  will  be  lacking  in  oxygen 
and  have  far  too  much  carbonic  dioxide.  It  would  be 
only  a  question  of  time,  if  all  openings  were  closed  so 
that  the  air  in  the  room  could  not  either  get  out  nor 
fresh  air  get  in,  before  death  would  result.  This  would 
occur  in  a  short  time,  if  the  room  were  quite  small. 

Ventilation.  —  Thus  rooms  in  which  people  live  must 
be  so  arranged  that  the  air  can  be  changed  in  them. 
The  changing  of  the  air  in  a  room  is  called  'ventilation. 
Out  of  doors  the  movements  of  air,  winds,  and  currents 
provide  a  perfect  ventilation.  To  get  good  ventila- 
tion in  a  room  or  house  it  is  important  to  know  how 


VENTILA  TION  I O/ 

much  air  should  be  supplied  to  each  person.  We  will 
now  see  how  currents  of  air  may  be  made  so  that  the 
air  will  flow  in  and  out  of  the  room  and  give  the  needed 
supply. 

Those  who  have  studied  this  question  by  taking  the 
amount  of  air  made  impure  by  a  single  breath  and 
noting  that  there  are  seventeen  or  eighteen  breaths  in 
a  minute  tell  us  that  there  ought  to  be  supplied  to 
each  grown  person  from  3000  to  3500  cubic  feet  of  air 
each  hour,  and  to  each  child  not  less  than  2000  cubic 
feet  of  air  per  hour.  Since  the  body  when  actively 
at  work  uses  more  oxygen  and  throws  off  more  car- 
bonic dioxide  than  when  at  rest,  it  will  need  a  greater 
supply  of  air  than  the  resting  body.  To  illustrate 
what  these  figures  mean,  an  example  might  be  used. 
Three  thousand  cubic  feet  would  be  represented  by  a 
room  10  feet  high  with  a  floor  20  feet  long  and  15  feet 
wide.  Now  if  one  person  were  working  in  this  room, 
the  ventilation  should  be  good  enough  to  change  all 
the  air  in  it  once  every  hour.  If  two  were  working  in 
the  room,  the  ventilation  should  be  good  enough  to 
change  the  whole  of  the  air  in  it  every  half  hour.  Or  if 
four  persons  were  working  in  the  room,  the  air  should 
be  changed  every  fifteen  minutes,  and  so  on.  You  can 
calculate  the  number  of  cubic  feet  in  your  schoolroom; 
and  then,  taking  into  account  the  number  of  pupils 
in  the  room,  you  can  see  how  often  the  whole  air  in  the 
room  should  be  changed.  You  can  thus  see  whether 
the  ventilation  is  good  enough  for  the  number  in  the 
room. 

Many  schools,  workshops,  and  rooms  where  people 
gather  for  various  purposes  are  very  badly  ventilated. 


108     PURE  AIR,   BREATHING,   AND    VENTILATION 

Either  not  enough  space  is  given  to  each  person  or  not 
enough  air  is  supplied  to  keep  the  air  good.  Sleeping 
rooms  are  often  too  close,  as  well  as  the  living  rooms  of 
the  home.  Great  care  should  be  taken  to  have  the 
ventilation  in  all  these  right.  There  is  no  harm  in 
"  night  air  "  as  some  seem  to  think.  Out-of-door  air 
is  pure  even  at  night,  while  indoor  air  at  night  in  a 
poorly  ventilated  room  may  become  very  bad. 

How  to  secure  Ventilation.  —  One  way  of  removing 
the  air  and  bringing  in  new  air  is  by  pumps  or  fans 
run  by  machinery.  These  are  sometimes  used  in 
mines  or  in  large  buildings,  but  are,  of  course,  out  of 
the  question  in  most  buildings 
and  ordinary  homes.  We  have 
to  make  use  of  the  currents 
formed  in  the  air,  by  which 
streams  of  air  can  be  made  to 
flow  into  and  out  of  the  rooms. 
Now  how  are  currents  in  air 
made?  If  you  examine  the  air 


Fig.  46.  about  a  stove,  or  a  lamp,  when  it 

DIAGRAM  OF  THE  CURRENTS  OF     Js  heated,  yOU  will  find  that  there 

AlR    IN    A     ROOM     HEATED     BY  .  .     . 

A  STOVE,  s.  ALL  OPENINGS  is  a  current  of  air  rapidly  rising 
over  the  stove,  and  that  other  cur- 
rents near  the  floor  are  moving  toward  the  stove.  It  is 
the  same  with  the  lamp.  The  cause  of  these  currents 
is  this:  when  air  is  heated  it  expands.  If  a  certain 
amount  of  air  is  expanded,  it  will  be  lighter  than  the  rest 
of  the  air  about  it,  and  the  lighter  will  rise  in  the  heavier 
like  a  cork  in  water.  Hot-air  balloons  rise  because 
the  heated  air  in  them  is  lighter  than  the  air  around 
them.  All  the  large  currents  of  air  out  of  doors  which 


HOW   TO   SECURE    VENTILATION 


we  call  winds  or  breezes  are  made  in  the  same  way. 
The  sun  warms  some  part  of  the  earth  and  makes 
the  air  next  to  it  warm.  This  expands  it,  makes  it 
lighter,  and  the  cooler,  heavier  air  moves  underneath 
it  and  forces  it  up.  When  currents  are  started  in 
one  place,  these  cause  others  to  form  in  other  places. 
As  the  sun  shines  on  most  of  the  earth  every  day,  these 
changes  are  all  the  time  going  on  out  of  doors,  and 
thus  currents  of  air  are  all  the  time  moving  all  over  the 
face  of  the  earth,  making  a  perfect  ventilation.  If  we 
always  remember  that  warm  air  is  lighter  than  cool 
air  and  will  rise  in  it,  we  can 
always  tell  just  how  the  currents 
of  air  will  be  moving  in  a  room. 
As  just  seen,  air  will  always 
rise  from  a  heated  stove  or  radi- 
ator, and  cooler  air  will  move 
toward  it.  If  the  air  in  a 
room  is  warmer  than  the  air  out- 
side, a  window  open  at  the  top 
and  at  the  bottom  will  allow  the  F'9'  4G- 

,    ,i  CURRENTS  OF  AIR  IN  A   ROOM 

warm  air  to  go  out  at  the  top  as  HEATED  BY  A  STOVE>  St  WlN. 
the  cool  air  comes  in  at  the  lower  DOW  OPEN  AT  Top  AND  BOT- 

TOM. 

opening.     If  it  is  only  open  at  the 

top,  the  warm  air  will  go  out  at  that  opening  and  cold  air 
will  come  in  at  the  cracks  about  the  door,  windows,  or 
floor  that  are  lower  than  the  opening.  In  other  words, 
in  a  warm  room  warm  air  is  all  the  time  leaving  by  all 
openings  in  the  upper  part  of  the  room,  and  cool  air 
is  coming  in  by  all  openings  in  the  lower  part  of  the 
room.  If  the  air  in  the  room  is  colder  than  the  out- 
side air,  just  the  opposite  takes  place;  the  cold  air 


1 10    PURE   AIR,   BREATHING,   AND   VENTILATION 

leaves  by  the  lower  openings  and  warmer  air  comes  in 
by  the  upper  openings.  If  the  air  in  the  room  is  just 
as  warm  as  the  outside  air,  no  currents  will  take  place 
by  natural  means.  Ventilation  can  then  only  be  secured 
by  fanning  or  pumping  the  air  in.  Now  these  facts 
show  that  it  is  easiest  to  ventilate  a  room  when  it  is 
warmer  than  the  outside  air.  On  a  cold  day  in  winter 
small  openings  will  serve  as  well  to  change  the  air  in  a 
room  as  wide  open  windows  would  on  a  warm  day  in 
summer.  We  can  see,  too,  how  it  is  difficult  to  keep 
the  room  warm  and  at  the  same  time  well  ventilated 
in  winter,  or  cool  and  at  the  same  time  well  ventilated 
in  summer.  In  winter  the  warm  air  is  escaping  and 
cold  air  is  coming  in,  in  summer  the  cooler  air  is  escap- 
ing and  the  warm  air  is  coming  in. 

Some  houses  are  arranged  so  that  the  air  from  the 
oustide  is  brought  in  just  under  the  stove  or  radia- 
tor, and  by  this  means  it  is  heated  as  it  comes  into  the 
room.  Hot-air  furnaces  bring  warm  air  into  the  room 
from  without.  This  air  is  pure  if  the  outside  supply 
to  the  furnace  is  good.  When  a  room  is  heated  by  a 
furnace,  then  the  upper  openings  in  the  room  should 
be  kept  closed,  and  the  lower  ones  opened.  The  warm 
air  comes  in  and  pushes  the  cooler  air,  which  is  also 
less  pure,  out  of  the  lower  openings.  Thus  ventilation 
is  secured  without  loss  of  so  much  of  the  warm  air. 
Openings  in  the  upper  part  of  a  room  heated  by  a 
furnace  allow  both  the  warm  air  and  the  pure  air  to 
escape.  In  whatever  house  one  lives,  in  whatever  room 
he  works  or  spends  much  of  his  time,  and  especially  in 
his  sleeping  room,  he  should  examine  the  means  of 
heating  and  ventilation,  and  then  study  how  to  arrange 


HO W    TO   SECURE    VENTILATION 


III 


Fig.  47. 


CURRENTS  IN  A  ROOM  HEATED 
BY  A  HOT-AIR  FURNACE.  WIN- 
DOW OPEN  AT  BOTTOM.  AIR 
ENTERS  FROM  FURNACE  AT  F. 


everything  to  have  an  abundant  supply  of  air  passing 
through  the  room.  This  should  not  be  less  than  3000  to 
3500  cubic  jeet  per  hour  jor  a  _ 
grown  person  or  2000  jor  a  child. 
As  every  room  used  will  be  some- 
what different,  each  one  must  be 
examined  and  arranged  for. 

In  schoolhouses,  factories,  and 
other  buildings  where  numbers 
of  people  are  brought  together 
those  skilled  in  the  knowledge  of 
ventilation  should  be  employed 
to  plan  the  buildings.  It  often 
happens  that  a  schoolroom  must 
have  in  it  a  large  number  of 
pupils,  with  not  enough  space 
for  each  and  no  way  of  ventilating  except  by  windows 
and  doors. 

On  a  cold  day  the  opening  of  windows  or  doors  will 
cause  a  cold  draft  on  some  of  the  pupils,  which  is 
of  course  very  dangerous  for  them.  Keeping  all  open- 
ings closed  is  also  harmful.  This  is  a  very  bad  arrange- 
ment, as  the  room  should  be  dangerous  to  no  one. 
Those  in  power  should  seek  to  remedy  the  difficulty  as 
soon  as  possible ;  but  until  this  is  done  the  teacher  and 
pupils  will  have  to  manage  the  ventilation  as  best  they  can. 

By  experiment  it  should  be  determined  which  win- 
dows and  doors  can  be  opened  to  give  ventilation  and 
the  least  draft.  Then  every  hour  or  so  the  pupils  can 
take  a  rest,  and  all  windows  should  be  opened  for  a 
short  time  to  clear  out  all  the  air.  The  drafts  are  not 
so  dangerous  if  the  pupils  are  moving  about.  Then 


112     PURE  AIR,   BREATHING,   AND    VENTILATION 

at  recess  all  can  leave  the  room,  and  the  windows  and 
doors  should  be  opened  until  the  air  is  thoroughly 
purified. 

Other  Impurities  in  Air.  —  Thus  far  we  have  spoken 
only  of  air  made  bad  by  breathing  it.  There  are 
other  sources  of  impurities  in  the  air.  .  When  a  candle, 
lamp,  or  gas  flame  is  burning  in  a  room  it  uses  up  oxy- 
gen quickly  and  throws  into  the  air  much  carbon  dioxide 
and  sometimes  other  gases  more  or  less  poisonous. 
This  is  especially  true  of  gas  flames.  When,  then, 
these  are  burning  in  rooms,  the  ventilation  must  be 
increased. 

Gases  that  come  from  sewers,  cesspools,  or  decaying 
materials  may  contain  poisonous  substances  or  germs 
of  disease.  Care  should  be  taken  that  no  such  places 
with  bad  gases  escaping  from  them  are  near  dwellings- 
Spaces  underneath  dwelling  houses  should  be  well 
ventilated;  otherwise  the  air  there  may  become  foul 
and  the  ventilation  of  the  house  is  sure  to  carry  it  up 
into  the  house  rooms. 

All  the  air  near  the  earth  about  dwelling  houses, 
along  streets  and  roads,  has  more  or  less  dust  in  it. 
Much  of  this  dust  is  harmless,  and  when  it  is  breathed 
into  the  lungs  settles  on  the  walls  of  the  air  passages, 
where  a  slow  current  of  mucus,  which  is  made  to  flow 
up  and  out  along  the  lining  of  the  walls,  will  carry  this 
dust  out  (see  Respiration).  But  the  dust  may  contain 
germs  of  disease,  which  may  thus  get  into  the  body 
through  the  lungs.  All  this  only  shows  still  stronger 
reasons  for  keeping  all  the  ground  under  and  about 
the  house  clean  and  free  from  all  these  sources  of  foul 
air  and  dust. 


METHOD    OF  BREATHING  113 

Where  houses  are  gathered  together  into  towns 
and  cities,  the  public  officers  look  after  keeping  the 
streets  and  alleys  clean.  Every  one  should  insist 
that  this  be  done,  and  help  in  doing  it. 

Effects  of  Impure  Air.  —  It  has  been  pointed  out 
that  death  would  soon  follow  if  a  person  were  confined 
in  a  small  and  perfectly  closed  room  without  any  ven- 
tilation. Living  in  rooms  poorly  ventilated  would  not 
produce  death  immediately,  but  would  lead  first  to  the 
contraction  of  diseases,  more  or  less  dangerous  as  the 
rooms  were  more  or  less  poorly  ventilated.  One  of 
the  surest  cures  for  many  diseases  is  life  in  the  open 
air,  which  insures  perfect  ventilation.  If  pure  air  can 
be  a  cure  for  these  diseases,  surely  pure  air  at  the  start 
would  have  prevented  them. 

Method  of  Breathing.  —  Even  with  plenty  of  good 
air,  habits  of  breathing  may  be  such  as  not  to  make 
the  best  use  of  the  air.  The  lungs  are  best  filled 
when  the  body  is  erect,  with  the  shoulders  thrown 
well  backward,  and  as  little  pressure  of  clothing  as 
possible  on  the  chest  or  abdomen.  Air  is  a  very 
light  substance,  and  a  little  pressure  will  easily  prevent 
the  full  amount  from  coming  into  the  lungs.  How 
foolish  to  interfere  at  all  with  so  important  a  thing  as 
breathing!  In  bed  we  should  take  such  a  position 
that  breathing  will  be  not  at  all  interfered  with,  and 
the  bed  clothing  should  not  rest  too  heavily  on  the 
body. 

It  is  good  to  form  a  habit  of  occasionally  taking 
a  deep  breath  while  walking  or  exercising  in  the 
open  air.  By  this  means  all  parts  of  the  lungs  are 
well  expanded  and  rendered  active.  A  habit  of  stoop- 

IND.  PR.  PHYS.  —  8 


114     PURE  AIR,   BREATHING,   AND    VENTILATION 

ing  and  of  never  expanding  the  lungs  deeply  may  favor 
parts  becoming  feeble  or  diseased  from  little  use.  It 
is  certainly  most  important  to  cultivate  good  habits 
of  breathing.  No  part  of  Hygiene  is  more  essential 
than  that  concerning  pure  air,  good  ventilation,  and 
good  breathing. 

Tobacco  and  the  Lungs.  — The  most  usual  way  of 
using  tobacco  is  by  smoking,  which  is  done  by  drawing 
the  smoke  into  the  air  passages.  By  this  means 
vapors  of  the  burning  tobacco  pass  into  the  blood 
vessels.  Nicotine  is  among  these  vapors,  and  to  it  the 
particular  effects  of  tobacco  are  due.  There  are  other 
substances  among  the  vapors  which  have  an  injurious 
effect  either  on  the  blood  or  on  the  tissues.  The  most 
noticeable  effect  of  tobacco  is  on  the  heart  and  on  the 
nervous  system  rather  than  on  the  lungs  themselves. 

Asphyxia  is  the  term  applied  to  the  apparent  death 
which  may  occur  in  suffocation  from  immersion  in 
water  or  any  other  cause.  The  movements  of  respira- 
tion have  been  suspended,  and  death  may  soon  follow. 
The  course  to  be  taken  is  to  produce  artificial  respira- 
tion until  natural  respiration  returns.  The  following 
are  the  celebrated  directions  known  as: 

Marshall    Hall's    Ready    Method    in    Asphyxia.  - 
i  st.  Treat  the  patient  instantly  on  the  spot,  in  the 
open  air,  freely  exposing  the  face,  neck,  and 
chest  to  the  breeze,  except  in  severe  weather. 
2d.  In  order  to  clear  the  throat,   place  the  patient 
gently  on  the  face,  with  one  wrist  under  the 
forehead,  that  all  fluid,  and  the  tongue  itself, 
may  fall  forward,  and  leave  the  entrance  into 
the  windpipe  free. 


MARSHALL  HALVS  METHOD  IN  ASPHYXIA     115 

3d.  To  excite  respiration,  turn  the  patient  slightly 
on  his  side,  and  apply  some  irritating  or 
stimulating  agent  to  the  nostrils,  as  vera- 
trine,  dilute  ammonia,  etc. 

4th.  Make  the  face  warm  by  brisk  friction;  then 
dash  cold  water  upon  it. 

5th.  If  not  successful,  lose  no  time;  but,  to  imitate 
respiration,  place  the  patient  on  his  face,  and 
turn  the  body  gently,  but  completely,  on  the 
side,  and  a  little  beyond;  then  again  on  the 
face,  and  so  on,  alternately.  Repeat  these 
movements  deliberately  and  perseveringly, 
fifteen  times  only  in  a  minute.  (When  the 
patient  lies  on  the  thorax,  this  cavity  is 
compressed  by  the  weight  of  the  body,  and 
expiration  takes  place.  When  he  is  turned 
on  the  side,  this  pressure  is  removed,  and 
inspiration  occurs.) 

6th.  When  the  prone  position  is  resumed,  make  a 
uniform  and  efficient  pressure  along  the  spine, 
removing  the  pressure  immediately  before 
rotation  on  the  side.  (The  pressure  aug- 
ments the  expiration;  the  rotation  com- 
mences inspiration.)  Continue  these  meas- 
ures. 

yth.  Rub  the  limbs  upward,  with  firm  pressure  and 
with  energy  (the  object  being  to  aid  the 
return  of  venous  blood  to  the  heart). 

8th.  If  possible,  substitute  for  the  patient's  wet 
clothing  such  other  covering  as  can  be  in- 
stantly procured,  each  bystander  supplying 
a  coat  or  a  cloak,  etc.  Meantime,  and  from 


Il6    PURE  AIR,   BREATHING,   AND    VENTILATION 

time   to   time,    to   excite  inspiration,   let   the 

surface  of  the  body  be  slapped  briskly  with 

the  hand. 
Qth.  Rub  the  body  briskly  till  it  is  dry  and  warm; 

then  dash  cold  water  upon  it  and  repeat  the 

rubbing. 

Avoid  the  immediate  removal  of  the  patient,  as  it 
involves  a  dangerous  loss  of  time;  also,  the  use  of 
bellows,  or  any  forcing  instrument;  also,  the  warm 
bath  and  all  rough  treatment. 


CHAPTER  XII 

THE   SKIN   AND   THE   KIDNEYS 

The  covering  of  the  body  is  one  of  the  most  im- 
portant, and  at  the  same  time  one  of  the  most  inter- 
esting, organs  to  study.  It  has,  as  we  shall  see  pres- 
ently, several  important  uses.  The  one  which  is  most 
evident  is  that  of  protecting  the  parts  below  it  from 
mechanical  injuries.  In  this  way  it  acts  as  a  strong 
suit  of  clothing  —  flexible  and  yielding,  yet  not  easily 
broken  or  torn. 

General  View.  — The  skin  is  of  a  very  complex 
structure.  It  consists  of  two  layers,  which  are  so 
arranged  as  to  support  very  many  different  organs. 
Fig.  48  is  a  considerably  magnified  representation  of  a 
section  made  vertically  through  the  skin.  The  whole 
skin  is  about  one  tenth  of  an  inch  thick,  or  less  in 
many  parts.  It  is  thickest  on  the  palms  of  the  hands 
and  soles  of  the  feet;  and  is  thinnest  at  the  joints 
and  wherever  rapid  motions  are  required,  as  over  the 
eyelids. 

Structure  of  the  Skin.  — The  skin  is  composed  of 
two  layers,  as  shown  in  the  figure.  The  outer  layer 
is  called  the  epidermis.  It  forms  a  thjn  covering  over 
the  dermis.  The  epidermis  has  no  blood  vessels  in  it, 
and  as  to  nerves,  it  has  only  the  smallest  nerve  fibrils 
in  its  lowest  parts.  It  forms  a  layer  that  will  not  let 

117 


THE  SKIN  AND    THE  KIDNEYS 


water  pass  through  it  either  into  or  out  from  the  body. 
It  prevents  poisonous  substances  from  passing  into  the 
body,  and  furnishes  proper  covering  for  the  ends  of 

the  nerves  of  touch  and   of 
temperature. 

Growth  of  the  Epidermis.— 
The  epidermis  grows  in  its 
lower  layer  of  cells,  which 
crowd  on  those  that  lie  above 
and  push  them  out.  The 
outer  layers  are  constantly 
wearing  away.  Thus  one's 
skin  is  always  a  comparatively 
fresh  one. 

The  Dennis. — The  lower 
layer  of  the  skin  is  the  der- 
mis.  It  is  composed  of  a 
closely  woven  sheet  of  connec- 
tive tissue.  In  it  are  placed 
great  numbers  of  blood  ves- 
sels, a  network  of  nerves,  a 
network  of  lymphatic  vessels, 
Fig,  48.  immense  numbers  of  sweat 

SECTION  OF  THE  SKIN.    MAGNIFIED,    glands,     the      sheaths      of      the 

roots    of    hairs,    and    the   oil 
glands. 

When  the  skin  of  an  animal  is  made  into  leather 
it  is  mainly  the  connective  tissue  of  the  dermis  that 
is  tanned. 

The  dermis  is  tied  fast  to  the  rest  of  the  body  by 
a  layer  of  connective  tissue.  It  is  so  fastened  that  it 
may  be  loose  enough  to  be  pushed  about  a  little  over 


H,  hair;    E,  epidermis;    D,   der- 
mis;   P,   papillae;    S,   mouth  of 
sweat  gland;   O,  oil  gland. 


FAT  IN   THE   SKIN  II 9 

each  point,  and  at  the  same  time  be  pretty  firmly 
held  in  place  over  the  whole  body.  The  skin  is  really 
stronger  and  tougher  than  one  might  suppose  from  its 
appearance. 

Papillae.  — The  upper  surface  of  the  dermis  is  raised 
into  an  immense  number  of  small  projections  called 
papilla.  Fig.  49  shows  some 
from  the  palm  of  the  hand  from 
which  the  epidermis  has  been  re- 
moved. These  are  found  every- 
where in  the  skin,  but  are  most 
numerous  on  the  palms  of  the  F'9-  49- 

hands  and  the  soles  of  the  feet. 

The   epidermis  fits  Closely  Over         AMOVED.    MAGNIFIED. 

these  and  so  nearly  levels  up  the  space  between  them 
that  their  existence  would  not  be  known  if  viewed  from 
the  surface  of  the  skin. 

But  on  the  palms  of  the  hands  and  soles  of  the 
feet  the  epidermis  can  be  seen  to  be  in  fine  parallel 
ridges.  These  ridges  are  over  rows  of  papillae,  just 
beneath  in  the  dermis.  The  papillae  are  shown  both 
in  Fig.  48  and  Fig.  49.  In  each  papilla  is  a  capillary 
blood  vessel  and  a  network  of  nerves,  and  in  very  many 
a  minute,  curiously  formed  body  in  which  a  nerve 
ends,  which  may  be  a  nerve  of  touch  or  one  of 
temperature. 

Fat  in  the  Skin.  —  In  the  lower  layer  of  the  dermis, 
in  the  meshes  of  the  connective  tissue,  are  many  little 
globules  of  fat.  Sometimes  the  fat  may  increase  to 
such  an  extent  as  to  make  a  thick  layer  between  the 
skin  and  the  muscles  and  other  parts  beneath.  When 
this  is  the  case  the  body  is  more  rounded  in  outline. 


I2O  THE   SKIN  AND    THE   KIDNEYS 

This  layer  of  fat  serves  to  lessen  the  effects  of  blows 
on  the  body  and  helps  to  keep  it  warm. 

In  some  of  the  lower  animals,  such  as  seals  and 
whales,  this  layer  is  enormously  developed.  In  the 
whale  it  is  known  as  the  blubber.  This  arrangement 
allows  these  animals  to  live  in  extremely  cold  climates, 
and  in  the  case  of  seals  and  walruses,  to  bear  the 
rough  contact  with  rocks  and  ice  which  the  manner 
of  life  of  a  seal  or  walrus  requires.  The  large  amount 
of  fat  found  in  these  animals  causes  them  to  be  hunted 
for  their  oil. 

The  Sweat  Glands.  —  A  sweat  gland,  Fig.  48,  is 
formed  of  a  knot  of  a  coiled  tube  placed  in  the  lower 
layer  of  the  dermis.  It  is  connected  with  the  outer 
surface  of  the  skin  by  a  continuation  of  its  tube  through 
the  two  layers  of  the  skin. 

The  coiled  part  secretes  the  sweat  or  perspiration, 
which,  carried  to  the  surface,  is  poured  out,  to  evapo- 
rate completely  if  it  comes  out  slowly,  or  to  gather 
into  drops  if  it  flows  out  rapidly. 

The  secretion  of  the  sweat  is  regulated  by  nerve 
fibers  which  come  to  the  coiled  part.  The  material 
of  the  perspiration,  which  is  mostly  water,  is  fur- 
nished by  the  blood  flowing  through  a  network  of 
capillaries  inclosing  the  coiled  tube. 

Perspiration  and  the  Temperature  of  the  Body.  - 
Each  one  knows  well  that  rapid  running  or  exercise 
of  any  kind,  or  even  very  little  exercise  on  a  very  hot 
day,  will  cause  the  sweat  to  form  in  large  quantities 
over  the  surface  of  the  body. 

Now,  as  this  always  occurs  under  the  same  cir- 
cumstances, it  might  be  supposed  that  there  is  some 


REGULA TION  OF  THE  TEMPERA TURE  OF  BODY     121 

reason  for  the  connection  of  the  two  occurrences. 
And  such  is  the  case. 

Source  of  Heat  in  the  Body.  —  Let  it  be  recalled 
that  the  increase  of  motion  of  the  body  can  occur  only 
by  increase  of  the  oxidations.  This  increase  we  found 
always  to  be  accompanied  by  the  production  of  heat. 
Increase  of  activity  of  any  tissue  increases  the  amount 
of  heat  in  the  body.  When  the  digestion  is  most  active, 
it  is  found  that  the  blood  coming  away  from  the  diges- 
tive organs  is  warmer  than  that  going  to  them.  Besides 
the  heat  produced  in  connection  with  the  usual  activi- 
ties of  the  tissues,  the  body  has  the  power  to  produce 
oxidations  in  some  of  the  tissues  for  the  sole  purpose 
of  increasing  the  heat. 

The  body  is  so  constructed  that  it  works  best  at  a 
temperature  of  98°  Fahr.  If  the  temperature  rises 
above  that  limit  only  one  or  two  degrees,  there  is 
something  wrong,  and  if  it  mounts  two. or  three  degrees 
still  higher,  life  is  in  danger.  If  it  fall  much  below 
98°,  it  is  also  in  danger. 

Regulation  of  the  Temperature  of  the  Body.  — 
Now,  special  activity  in  the  muscles  in  vigorous  exer- 
cise produces  heat  which  would  raise  the  temperature 
higher  than  98°  if  there  were  not  a  way  to  reduce  it 
by  some  pooling  process.  This  process  is  by  evapo- 
ration of  the  water  of  the  sweat. 

Evaporation  is  a  very  effective  means  of  cooling. 
It  requires  a  large  amount  of  heat  to  evaporate  a 
small  amount  of  water. 

This  is  shown  by  placing  a  moist  cloth  on  the  bulb 
of  a  thermometer.  As  the  cloth  dries,  the  mercury 
shows,  by  falling  several  degrees,  that  it  is  cooled.  If 


122  THE   SKIN  AND    THE   KIDNEYS 

some  substance  like  gasolene  or  ether,  which  evapo- 
rates more  quickly,  is  used,  a  very  low  temperature 
can  be  produced,  even  though  the  experiment  is  car- 
ried on  in  a  warm  atmosphere. 

The  sweat  glands  are  all  the  time  sending  out  water, 
which  generally  evaporates  as  soon  as  it  reaches  the 
surface.  When  an  increase  of  heat  in  the  body  that 
might  bring  the  temperature  of  the  body  above  98° 
Fahr.  occurs,  the  nerves  stimulate  the  glands  to  work, 
and  thus  to  pour  out  a  greater  amount  of  sweat.  The 
amount  sent  out  will  be  according  to  what  may  be 
needed  at  that  particular  time  to  cool  the  body  suf- 
ficiently to  overcome  the  increase  in  the  heat. 

This  arrangement  must  act  very  promptly  and  very 
perfectly,  so  that  the  body  may  keep  the  same  degree 
of  temperature  on  going  from  a  cold  room  to  a  warm 
room,  or  from  a  cold  day  to  a  warm  day,  or  from  one 
season  to  another. 

We  may  say,  then,  that  one  of  the  most  important 
uses  of  the  sweat  glands  is  to  regulate  the  temperature 
of  the  body. 

Perspiration  as  a  Secretion.  —  The  sweat  is  mostly 
water,  but  as  it  passes  out  it  carries  a  very  small  amount 
of  salines  and  a  small  amount  of  organic  substances. 
These  are  regarded  as  excretions  to  be  cast  ^ut  of  the 
body. 

The  Skin  as  an  Organ  of  Touch  and  Temperature.  - 
In  the  skin,  as  was  mentioned,  the  nerves  of  sensation 
end  in  special  organs,  which  are  affected,  the  one  by 
pressure,  the  other  by  change  in  temperature. 

By  means  of  these  bodies,  the  skin  becomes  an 
organ  with  the  important  duty  of  giving  the  knowledge 


USES   OF  THE  SKIN  12$ 

obtained  from  these  senses.  It  thus  becomes  a  con- 
stant guard,  both  to  warn  us  of  all  danger,  and  to  give 
us  the  information  needed  at  every  moment  of  our 
existence. 

The  Hair.  —  The  hairs  are  really  epidermis  grown 
out  into  long  threads.  Each  one  forms  on  the  top  of 
a  special  papilla.  This  papilla  is  very  much  like  any 
other  papilla,  except  that  it  is  at  the  bottom  of  a  little 
pit.  See  Fig.  48. 

The  cap  of  epidermis  (which  is  formed  over  it )  re- 
mains, new  portions  being  formed  beneath  it,  and  so 
on  until  it  becomes  a  very  slender,  but,  in  some  cases, 
an  enormously  elongated  rod  of  epidermis. 

Minute  hairs  are  scattered  all  over  the  body.  A 
little  experiment  with  some  of  them,  say  those  on  the 
back  of  the  hand,  will  show  that  they  greatly  aid  in 
touch.  Each  one  has  a  nerve  at  the  bottom  of  its 
papilla. 

The  Nails.  — The  nails  are  thick  plates  of  epidermis 
growing  out  from  a  number  of  papillae.  They  grow 
continually,  and  thus  provide  for  a  comparatively 
new  nail  all  the  time.  One  may  determine  the  rate 
of  growth  by  making  a  line  on  one  and  observing 
the  number  of  days  it  takes  to  move  a  certain  dis- 
tance. The  use  of  the  nails  is  made  very  plain  in 
attempting  to  take  hold  of  very  small  objects. 

Uses  of  the  Skin.  —  We  may  sum  up  the  most  im- 
portant uses  of  the  skin  as  follows: 

i st.  It  makes  a  strong  suit  of  clothing  to  protect  the 
body  against  mechanical  injuries. 

2d.  It  prevents  the  absorption  of  injurious  sub- 
stances from  without. 


124  THE   SKIN  AND    THE  KIDNEYS 

3d.  It  prevents  evaporation,  except  under  control. 

4th.  It  helps  regulate  the  temperature  of  the  body. 

5th.  It  gives  us,  through  the  organs  of  sense  in  it, 
very  important  and  really  necessary  knowledge. 

The  Kidneys.  —  It  may  be  repeated  here  that  from 
the  changes  that  take  place  in  the  body,  the  three 
principal  wastes  are: 

i st.  Carbon  dioxide,  which  is  got  rid  of  mainly  at 
the  lungs ; 

2d.  Water,  which  is  principally  thrown  off  at  the 
skin ;  and 

3d.  The  waste  containing  nitrogen,  a  substance 
something  like  ammonia,  called  urea,  which 
is  thrown  off  by  the  kidneys. 

The  kidneys  are  placed  one  on  each  side  of  the 
spinal  column  in  the  abdominal  cavity,  near  the  last 
dorsal  and  the  two  or  three  upper  lumbar  vertebras. 
They  are  large  glands,  through  which  a  great  amount 
of  blood  passes.  They  separate  from  the  blood  that 
goes  through  them  certain  substances  dissolved  in 
water.  The  principal  one  is  urea. 

These  substances  are  removed  from  the  body. 
Thus  the  blood  in  its  circuit  passes  the  lungs,  where 
it  loses  carbon  dioxide ;  the  kidneys,  where  it  loses 
urea;  and  the  skin,  where  it  loses  water.  If  any  one 
of  these  excretions  be  stopped,  the  result  will  be  fatal. 


CHAPTER  XIII 

CARE  OF  THE  SKIN 

THE  uses  of  the  skin  just  learned  show  us  how  im- 
portant an  organ  it  is  and  guide  us  in  the  kind  of  care 
to  give  it. 

First  of  all  it  should  be  kept  clean.  The  dirt  that 
gathers  on  the  skin  is  of  two  classes :  that  which  comes 
from  the  body  itself  in  perspiration,  and  that  which 
gathers  on  it  from  outside  sources.  The  gathering  of 
the  latter  may  in  time  interfere  with  the  secretion  of 
the  perspiration.  This  would  be  harmful  because  it 
would  hinder  the  best  regulation  of  the  temperature. 
It  would  also  be  injurious  to  the  body  to  stop  any 
part  of  the  excretion  of  the  poisonous  wastes  that  are 
thrown  out  with  the  sweat.  The  dirt  which  gathers 
from  outside  sources  is  dangerous  to  the  body,  be- 
cause it  may  contain  harmful  bacteria,  which  a  break 
in  the  skin  by  a  scratch  or  wound  may  permit  to  get 
into  the  body  and  produce  some  kind  of  disease  (see 
Chapter  XIX  on  Disease).  For  these  reasons  the  im- 
portance of  keeping  the  skin  clean  is  very  plain.  A 
body  with  a  clean  skin  is  much  safer  from  disease 
than  one  which  is  not  clean. 

Bathing.  —  Thus  we  see  there  are  very  important 
physiological  reasons  for  bathing  besides  the  equally 

I25 


126  CARE    OF   THE   SKIN 

important  one  that  good  breeding  requires  cleanliness 
of  the  body.  No  definite  rules  for  bathing  suitable  for 
everybody  can  be  laid  down,  because  occupations  of 
people  differ  so  greatly.  The  hands  and  face,  being  the 
most  exposed,  naturally  must  be  bathed  frequently.  The 
whole  body,  except  the  scalp,  should  be  washed  daily 
and  a  bath  should  be  taken  at  least  once  a  week,  and 
as  much  oftener  as  possible.  To  remove  thoroughly 
the  substances  accumulating  on  the  skin,  warm  water 
and  a  little  soap  are  necessary.  The  soap  ought  to 
be  pure  and  of  a  good  quality,  for  there  are  soaps 
with  substances  in  them  that  injure  the  skin  rather 
than  help  it.  The  bath  is,  of  course,  made  use  of 
for  other  purposes  besides  that  of  keeping  the  body 
clean.  Bathing  in  summer  in  streams,  ponds,  and  at 
the  seashore  is  for  pleasure,  and  it  is  a  very  healthful 
form  of  sport  and  exercise.  There  are  many  forms 
of  baths  used  for  special  purposes.  The  experience 
of  very  large  numbers  of  people  show  that  a  very  health- 
ful habit  to  form  is  that  of  taking  a  bath  in  cool  water 
every  day.  It  should  be  done  very  quickly  and  the 
skin  should  be  thoroughly  rubbed.  This  quickens 
the  circulation  in  the  skin  and  improves  its  condition, 
and  through  it  benefits  the  whole  body.  Every  dwell- 
ing house,  no  matter  how  small,  ought  to  have  a  bath 
room,  so  that  bathing  will  not  be  neglected  for  lack  of 
convenience. 

Hair  and  Nails.  — The  most  important  thing  in  the 
care  of  the  hair  is  that  the  scalp  should  be  thoroughly 
washed  and  afterward  rubbed  dry,  "  shampooed  "  as 
it  is  called,  at  least  twice  a  month.  Oftener  would  be 
better.  This  is  the  best  thing  to  be  done  to  keep  the 


CLOTHING  127 

scalp  and  hair  in  a  healthy  condition.  The  dirt  accumu- 
lating under  the  nails  is  dangerous,  for  it  may  contain 
disease  germs  which  a  splinter  might  push  into  the 
finger. 

Clothing.  —  By  the  use  of  clothing  man  can  make 
himself  comfortable  in  all  kinds  of  climate,  which  is 
impossible  for  the  lower  animals.  Thus,  man  can  be 
active  and  carry  on  his  work  in  every  part  of  the  world 
and  in  all  seasons.  There  are  many  uses  of  clothing. 
Clothing  covering  the  body  helps  to  keep  the  heat  from 
being  lost  from  it.  Consequently  in  cold  air  clothing 
allows  a  great  saving  of  energy  and  of  food.  But 
when  one  is  exposed  to  the  scorching  rays  of  the 
sun,  the  clothing  protects  the  body  from  the  heat. 

Clothing  also  protects  the  body  from  injury  from 
external  things.  It  saves  the  body  many  a  bruise  and 
scratch.  For  example,  scrambling  through  a  thicket 
of  brush  would  be  a  painful  exercise  without  clothing. 
Even  in  ordinary  life  about  the  shop,  farm,  or  house, 
clothing  helps  us  much  in  this  way.  The  hunter  and  the 
football  player  often  have  special  kinds  of  clothing 
to  protect  their  bodies. 

Clothing  is,  of  course,  used  also  from  custom  and  for 
ornament.  Wrong  use  of  clothing  may  become  the 
source  of  ill  health.  For  example,  if  a  boy  on  the 
school  ground  by  playing  hard  becomes  warm,  and 
then  takes  off  his  coat  and  sits  in  a  cool  place  to  cool 
off,  he  is  in  great  danger  of  taking  cold.  It  would  be 
better  to  take  off  the  coat  to  play,  and  put  it  on  when 
stopping,  and  thus  cool  off  more  gradually. 

Sometimes  one  who  is  accustomed  to  a  warm,  com- 
fortable dress  will  on  some  special  occasion  change 


128  CARE   OF  THE   SKIN 

it  for  a  very  thin  one,  and  thus  run  great  risk  of  a  cold 
or  of  even  more  severe  illness,  as,  for  example,  pneu- 
monia. 

Long  experience  has  taught  people  what  kinds  of 
clothing  are  comfortable  at  different  seasons  and  in 
different  climates.  It  is  easy  to  learn  what  to  use  in 
each  case.  It  is  bad  to  get  into  a  habit  of  wearing  too 
much  clothing  for  the  season.  Nor  is  it  wise  to  go 
with  too  little  clothing  during  cold  weather.  In  other 
places  in  this  book  it  has  been  insisted  that  the  cloth- 
ing should  not  press  on  any  part  of  the  body  so  as 
to  interfere  with  circulation  or  respiration.  All  that 
has  been  said  regarding  the  necessity  of  keeping  the 
body  clean  applies  to  the  clothing,  especially  that  which 
comes  in  contact  with  the  skin. 

Clothing  for  the  Feet.  —  As  the  feet  must  constantly 
strike  the  hard,  rough  ground  and  go  through  water, 
mud,  ice,  and  snow,  we  have  long  ago  learned  to 
give  them  especial  care  in  clothing.  But  often  wrong 
things  are  done  with  the  foot  coverings.  For  ex- 
ample, thin  shoes  and  stockings,  which  in  winter 
could  only  be  suitable  for  the  warm  house,  are  some- 
times worn  on  cold,  wet,  or  snowy  streets.  Even  with 
good  shoes  the  feet  may  become  wet,  and  if  one  remains 
for  a  long  time  in  a  cold,  damp  place  with  the  feet  in 
that  condition,  the  health  becomes  endangered.  The 
feet  should  be  kept  dry,  warm,  and  clean  as  much 
of  the  time  as  possible. 

As  for  shoes,  common  sense  would  teach  that  they 
should  be  adapted  to  conditions  in  which  we  must  use 
them.  They  should  always  fit  snugly  and  comfortably, 
and  never  compress  the  feet,  if  we  wish  well- formed 


CLOTHING  FOR    THE  FEET  I2Q 

feet  instead  of  deformed  feet,  with  painful  corns  and 
bunions.  The  habit  of  wearing  rubber  overshoes  in 
winter  in  the  wet  and  snow  is  a  very  good  one,  but 
they  should  be  kept  on  only  when  needed,  since  they 
keep  in  the  moisture  arising  from  the  foot  and  do  not 
allow  the  air  to  circulate. 


IND.  PR.  PHYS.  —  9 


CHAPTER  XIV 

THE  STRUCTURE  OF  THE  NERVOUS  SYSTEM 

All  Parts  of  the  Body  work  together  through  the 
Nervous  System.  —  In  our  first  lesson  it  was  noted 
that  in  any  movement  of  the  body  the  parts  worked 
together  in  some  sort  of  harmony.  The  boy  in  climb- 
ing a  tree  sees  a  limb  and  reaches  out  his  hand  for  it. 
In  this  action  the  eye  and  the  arm  must  have  some 
connection.  In  the  whole  action  the  feet,  legs,  hands, 
arms,  eye,  ear,  the  heart,  the  lungs,  and  very  many 
other  parts  of  the  body  work  with  each  other,  and  not 
against  each  other,  in  accomplishing  this  act. 

Now,  when  the  muscles  of  the  legs  are  in  greater 
activity,  the  heart  must  beat  more  vigorously.  This 
could  not  occur  if  there  were  not  some  means  of  com- 
munication between  them.  So  it  is  with  the  hun- 
dreds of  other  examples  that  might  be  given.  The 
means  of  communication  in  all  these  cases  is  the 
Nervous  System.  We  shall  try  to  see  as  clearly  as 
possible  how  this  is  the  case. 

Nerves  in  the  Arm.  —  In  studying  the  motions  of 
the  fingers  it  was  observed  that  nerves  pass  to  each 
muscle,  and  that  every  muscle  is  made  to  contract 
by  a  nervous  stimulus  sent  into  it.  What  this  stimu- 
lus is  like  it  would  be  hard  to  say. 

130 


NERVOUS  IMPULSES 


If  the  nerves  of  the  arm  could  be  exposed  as  shown 
in  the  figure,  and  a  single  nerve  be  cut,  then  the  will 
would  lose  all  power  to  cause  the  muscles  with  which 
the  nerve  is  connected  to  con- 
tract, and  at  the  same  time  a 
touch  on  the  hand  could  not 
be  felt.  Now,  if  the  end  of 
the  part  of  the  nerve  con- 
nected with  the  muscle  should 
be  pinched,  the  muscle  would 
contract  promptly.  If  the  end 
connected  with  the  brain  were 
pinched,  pain  would  be  felt. 

Nervous  Impulses. — This 
shows  that  the  nerves  conduct 
some  kind  of  energy  which, 
coming  into  the  muscle,  makes 
it  contract,  but  coming  into 
the  brain  causes  a  feeling  of 
pain,  touch,  or  other  sensation. 

What  these  nervous  impulses 
are  like  we  can  not  answer. 
In  electricity  we  have  an  ex- 
ample of  an  impulse,  which 
metal  wires  will  conduct  a  long 
distance.  By  its  means  an  in- 
strument in  one  city  may  be 
set  in  motion  by  a  movement 
in  a  distant  city. 

Nervous  impulses  act  something  like  the  electrical 
impulses,  but  still  it  is  not  thought  that  they  are  the 
same.  What  we  can  see  well  enough  is  that  they  do 


Fig.  50. 

NERVES  OF  THE  FOREARM. 

The  white  cords  are  the  nerves. 
The  shaded  tubes  are  arteries. 


132     THE   STRUCTURE    OF   THE  NERVOUS  SYSTEM 

for  the  body  what  the  electrical  currents  do  by  means 
of  the  wires  for  a  city. 

Nerves.  —  The  larger  nerves  look  like  white  cords. 
They  branch  into  smaller  and  smaller  white  threads, 
which  go  to  the  various  parts  of  the  body.  The  small- 
est branches  are  so  minute  that  they  can  not  be  seen 
without  a  microscope.  Fig.  50  shows  some  of  the 
larger  nerves  in  the  forearm  as  they  would  appear 
if  the  skin  and  some  of  the  muscles  were  removed. 
The  white  cords  in  the  picture  are  nerves  and  the 
shaded  ones  are  arteries. 

A  Nerve  Fiber.  — The  smallest  division  of  a  nerve 
is  a  nerve  fiber.  A  nerve  is  like  the  cable  sometimes 
used  in  a  telephone  system.  The  cable  is  made  up 
of  a  bundle  of  wires,  all  kept  separate  so  that  they  can 
not  touch  one  another,  but  bound  up  into  one  cable 
with  a  covering  to  protect  it  and  allow  it  to  be  fastened 
to  its  support.  It  finally  divides  up  into  separate  wires, 
which  run  to  the  separate  telephones  in  the  house.  So 
the  nerve  is  a  bundle  of  fibers,  which  finally  divides 
into  the  separate  fibers,  which  run  to  separate  muscle 
fibers,  or  to  separate  cells  in  a  sense  organ;  that  is, 
eye,  ear,  touch,  taste,  or  smell  organ.  If  a  single 
little  fiber  be  traced  from  a  muscle  or  eye  or  touch 
organ  in  the  skin  inward  toward  the  central  part  of 
the  body,  it  would  be  found  to  run  to  the  spinal  cord. 
Some  of  the  fibers  end  here  and  some  go  on  to  the 
brain.  In  the"  spinal  cord  and  in  the  brain  the  fibers 
are  connected  with  little  bodies  called  nerve  cells. 

There  are  many  thousands  of  nerve  cells  in  the  brain 
and  spinal  cord.  To  understand  better  how  these 
parts  are  arranged,  let  us  imagine  that  we  could  pick 


THE  NERVOUS  SYSTEM 


133 


up  one  of  the  tiny  nerve  cells  in  the  brain  and  spinal 
cord,  and  that  we  could  lift  it  out  without  breaking 
the  minute  fiber  to  which  it  is  attached,  and  then 
unravel  the  fiber  farther  through  the 
nerve  right  down  to  the  organ  to  which 
it  goes,  which  in  this  case  we  may  sup- 
pose is  a  muscle.  We  would  find  it 
attached  to  a  microscopic  bit  of  muscle, 
a  muscle  fiber.  If  this  little  bit  of  mus- 
cle were  taken  out  also,  and  magnified,  we 
should  have  the  arrangement  shown  in 
Fig.  51.  This  shows  how  the  cells  in 
the  spinal  cord  are  connected  with 
muscle  fibers  in  the  muscle.  Now  cells 
in  the  retina  of  the  eye,  certain  cells  in 
the  ear,  in  the  tongue,  in  certain  parts 
of  the  nasal  passages,  and  in  the  skjg> 
are  connected  in  the  same  way  with 
fibers  which  run  along  in  the  nerves 
until  they  come  to  the  spinal  cord  and 
the  brain.  In  this  way,  then,  the  fibers  DlAGRA'f '  T0  'SHOW 
connect  the  brain  and  spinal  cord  with  How  A  NERVE 
the  muscle  fibers  and  can  make  them 
move,  and  the  sense  organs  are  con- 
nected with  the  spinal  cord  and  brain,  and  by  the  fibers 
can  make  the  brain  feel. 

The  Nervous  System.  — The  brain,  spinal  cord,  and 
all  the  nerves  in  all  parts  of  the  body  taken  together 
are  called  the  nervous  system.  Fig.  52  gives  a  general 
view  of  how  the  parts  are  arranged.  The  brain  is  in 
the  skull,  the  spinal  cord  is  in  the  spinal  column.  The 
nerves  are  connected  with  the  brain  and  spinal  cord 


CELL  is  JOINED  TO 
A  MUSCLE  CELL 
BY  A  NERVE  FIBER. 


134     THE  STRUCTURE    OF  THE  NERVOUS  SYSTEM 


in  pairs.     Altogether  there  are  twelve  pairs  of  nerves 

connected  with  the  brain  and  thirty-one  pairs  with  the 

spinal  cord. 
The  Nerve  Cells.  —  The  nerve  cells  are  arranged  as 

a  thin  layer  on  the  outer  surface  of  the  brain,  and  in 

groups  in  the  lower 
parts  of  the  brain. 
They  also  form  the 
central  part  of  the 
spinal  cord.  There 
are  many  hundreds 
of  thousands  of 
these  tiny  nerve 
cells.  Because  they 
have  a  slight  shade 
of  color,  the  parts 
they  are  in  are 
called  the  "  gray 
matter."  The  nerve 
fibers  are  white,  and 
parts  of  the  brain 
Fig.  53.  and  spinal  cord  in 

BRAIN,  SEEN  FROM  ABOVE,  CEREBRUM  ONLY          which     they    He    are 

SHOWING.  11        1        j.1       '  T_'i 

called    the       white 

i,  longitudinal  fissure  separating  the  hemispheres  ; 
2,  frontal  lobes  of  the  cerebrum;    3,  posterior  lobes.    rn^ttCT." 

The  Spinal  Cord.  — The  spinal  cord  in  man  is  about 
as  large  around  as  the  little  finger,  and  eighteen  inches 
in  length.  It  continues  from  the  medulla  (Fig.  55),  at 
the  opening  in  the  occipital  bone,  to  about  the  second 
lumbar  vertebra.  Its  central  portion  is  occupied  by 
gray  matter ;  that  is,  the  nerve  cells.  Outside  of  these 
are  nerve  fibers,  making  up  its  white  matter.  The 


THE  BRAIN 


135 


-6 


roots  of  the  spinal  nerves  are  nerve  fibers,  most  of  which 
are  connected  with  the  cells  in  the  spinal  cord.  Many 
fibers  run  on  up  to  the  brain  just  outside  of  the 
core  of  nerve  cells.  The  spinal  cord  is  like  a  large 
nerve,  except  that  it  has  gray  matter  in  its  central 
portion. 

The  Brain.  —  The  brain  is  the  large  portion  of  the 
nervous  system  inclosed  in  the  cranium.  The  weight 
is  about  three 
and  one  fourth 
pounds.  Fig. 
53  shows  it, 
seen  from 
above;  and 
Fig.  54,  from 
below.  Fig. 
55  shows  a 
side  view  with 
certain  parts 
cut  through 
vertically. 

Of  the  parts 
shown  in  these 
views  the  cer- 
ebrum is  the 
largest  and  is  Fig.  54. 

also      the      UP-  BRAIN,  SEEN  FROM  BELOW. 

i.  TJ.         i,  longitudinal  fissure;  2  and  3,  front  and  posterior  lobes  of 

'^*-  L     the  cerebrum;    4,  cerebellum;   5,  optic  nerve;    6,   olfactory 

is  divided  into  1( 

the  right  and  left  hemispheres  by  a  deep  ditch,  called 
the  longitudinal  fissure.  Its  surface  is  broken  up  into 
many  curving  ridges,  which  are  called  the  convolu- 


136     THE   STRUCTURE    OF   THE  NERVOUS  SYSTEM 

tions.  They  are  shown  in  Figs.  53,  54,  and  55.  The 
part  which  is  like  a  stem  to  the  cerebrum  is  the  me- 
dulla oblongata,  MD  in  Fig.  55  and  7  in  Fig.  54. 

The  medulla  continues  down  into  the  spinal  column 
as  the  spinal  cord.  In  Fig.  55  that  portion  marked 
Sp  N,  to  which  the  roots  of  two  nerves  are  attached, 
is  a  part  of  the  spinal  cord. 

Attached  to  the  back  part  of  the  medulla,  close  up 

c 


Fig.  55. 

BRAIN  AND  CRANIAL  NERVES,  SEEN  PARTLY  IN  SECTION  AND  PARTLY  IN  SIDE  VIEW. 

C,  convolutions  of  the  cerebrum;  Cbl,  cerebellum  in  section;  MD,  medulla  oblon- 
gata; Sp  N,  spinal  nerves.  The  numbers  indicate  the  twelve  pairs  of  cranial  nerves 
in  their  order. 

to  the  cerebrum,  is  the  cerebellum.    This  is  shown  as 
cut  through  in  Fig.  55,  Cbl,  and  at  4  in  Fig.  54. 

At  the  base  of  the  cerebrum,  near  where  the  medulla 
joins  it,  are  several  parts  not  shown  in  the  figures, 
which  are  sometimes  referred  to  as  the  ganglia  at  the 
base  of  the  brain. 


THE   SYMPATHETIC  SYSTEM 


137 


In  Fig.  55  are  shown  the  twelve  pairs  of  cranial 
nerves,  which  are  often  known  by  the  terms 
first  cranial  nerve,  second,  third,  etc.  The 
most  important  of  these  are  the  following: 
The  first  pair  are  the  nerves  of  smell,  the 
second  pair  the  nerves  of  sight,  the  third 
pair  the  movers  of  the  eyeballs,  the  seventh 
pair  go  to  the  muscles  of  the  face  and  scalp, 
the  eighth  pair  are  the  nerves  of  hearing, 
the  ninth  pair  go  chiefly  to  the  tongue  and 
pharynx,  and  the  twelfth  pair  to  the  muscles 
of  the  tongue. 

The  Spinal  Nerves.  —  From  the  spinal 
cord  thirty-one  pairs  of  nerves  pass  out  to 
be  distributed  to  the  organs  of  the  body. 
Each  of  these  nerves  starts  from  two  roots, 
an  anterior  and  a  posterior  root,  which  soon 
join  together  to  make  one  nerve;  but  the 
nerve  soon  separates  into  a  great  number 
of  smaller  and  still  smaller  branches,  until, 
as  was  seen  in  a  former  section,  they  reach 
all  the  smallest  parts  of  each  organ. 

The  Sympathetic  System.  —  This  term  is 
applied  to  that  part  of  the  general  nervous 
system  which  consists  of  a  row  of  ganglia  on 
each  side  of  the  spinal  column,  and  the  net- 
work of  nerves  with  which  it  is  connected, 
that  run  all  through  the  body.  The  ganglia 
are  connected  with  each  other,  and,  through 
the  spinal  and  cranial  nerves,  with  the  spinal 
cord  and  the  brain.  It  is  really  not  a  sep- 
arate  system,  but  a  part  of  the  general  nervous  system. 


ATTA?HED.ES 


CHAPTER  XV 

HOW  THE  NERVOUS  SYSTEM  IS  USED.  CARE  OF  THE 
NERVOUS  SYSTEM 

How  the  People  of  a  Large  City  work  together  quickly. 
— If  one  examines  a  large  city  he  will  see  immense  num- 
bers of  wires  running  in  every  direction.  Large  groups 
of  wires  are  carried  by  poles  along  different  streets. 
Sometimes  they  are  bound  up  into  bundles  which  we 
call  cables.  These  may  be  carried  on  poles  or  they 
may  be  placed  under  the  ground.  Now  if  the  groups 
of  telephone  wires  be  followed  in  one  direction,  they 
will  be  found  to  be  coming  together  in  certain  places, 
which  we  call  the  central  telephone  exchanges.  If  we 
follow  the  wires  in  the  opposite  direction,  we  find  them 
ending  at  the  telephones  in  the  rooms  of  the  various 
houses.  Messages  are  continually  arriving  at  the  cen- 
tral stations  and  are  continually  going  out  from  them 
again.  By  this  means  an  immense  amount  of  busi- 
ness is  carried  on.  At  a  certain  house  groceries  are 
needed.  A  message  is  sent  in,  the  grocer  gets  it 
through  the  central  office,  and  brings  the  food  to 
the  house.  A  fire  occurs.  A  message  through  the 
central  office  brings  the  fire  engine.  Movements 
of  railroad  trains  are  managed  so  that  they  will 
not  run  into  one  another.  Meetings  are  arranged  at 
a  special  time  and  place  for  thousands  of  people  en- 

138 


ACTION  OF  THE  NERVOUS  SYSTEM  139 

gaged  in  thousands  of  transactions  which  require  the 
most  perfect  working  together  of  these  people.  The 
telephone  and  telegraph  systems  manage  this  for  us  in 
a  special  way.  The  postal  system  does  the  same  thing 
in  a  much  slower  way.  It  would  not  be  available  for 
fires  or  for  preventing  collision  of  trains,  but  it  is  a  good 
means  of  communication  where  rapidity  is  not  so  nec- 
essary. In  the  body  the  nervous  system  is  more  like 
the  telephone  and  telegraph  systems.  The  body  is  the 
city,  with  work  at  different  parts  going  on.  The  nerves 
are  the  wires.  The  brain  and  spinal  cord  are  the 
central  offices.  They  are  sometimes  called  the  central 
nervous  system. 

Action  of  the  Nervous  System.  —  It  has  already  been 
shown  that  the  nervous  system  is  an  arrangement  for 
allowing  the  different  parts  of  the  body  to  work  to- 
gether. We  have  just  seen  that  there  are  thousands 
upon  thousands  of  nerve  fibers  coming  into  the  spinal 
cord  and  brain  from  all  the  sense  organs,  and  that  there 
are  as  many  thousands  of  fibers  going  out  from  the  spinal 
cord  and  brain  to  the  muscles.  When  light  comes  to  the 
eye,  it  starts  a  nervous  impulse  in  the  retina;  this  goes 
over  the  nerve  fibers  to  the  brain.  We  see  the  object.. 
The  nervous  impulses  go  from  the  brain  down  to  the 
spinal  cord  and  out  to  the  nerves  until  they  reach  the 
muscles  of  the  arm  or  leg,  where  they  cause  motions, 
such  as  picking  up  an  object  or  walking  away  from  it. 
Thus  the  eye  is  able  to  guide  the  motions  of  the  body 
through  the  nervous  system.  This  is  what  is  meant 
by  the  eye  and  hand  working  together. 

In  the  same  way  sounds  may  guide  our  motions. 
Taste,  touch,  and  smell  may  tell  us  what  to  do. 


I4O       HOW   THE  NERVOUS  SYSTEM  IS   USED 

When  studying  the  circulation  and  respiration  it  was 
seen  that  the  heart  beats  faster  and  breathing  is  quicker 
when  the  body  is  thrown  into  vigorous  motions.  In  these 
cases,  nervous  impulses  come  into  some  part  of  the  cen- 
tral nervous  system  and  these  cause  impulses  to  go  out 
to  the  heart  and  muscles  for  breathing.  Thus  the  heart 
and  lungs  are  made  to  work  just  to  suit  the  working 
of  the  muscles.  In  this  way  perspiration  is  increased 
when  the  body  becomes  too  warm,  saliva  is  secreted 
when  food  is  placed  in  the  mouth,  gastric  juice  flows 
more  freely  when  food  is  in  the  stomach,  and  other 
secretions  occur  at  the  proper  time.  Thus  from  the 
different  parts  of  the  body  impulses  are  pouring  in  all 
the  time  into  the  central  nervous  system  and  pouring 
out  again  to  the  very  places  where  motions  and  secre- 
tions are  required  for  the  action  of  the  body  at  that 
moment.  In  this  way  we  see  that  the  complex  busi- 
ness of  the  body  is  carried  on  in  a  harmonious  way. 
The  parts  act  together  for  the  good  of  the  whole  body. 

Voluntary  Actions.  —  When  the  muscles  were  studied 
it  was  said  that  certain  muscles,  those  attached  to  the 
skeleton,  are  voluntary  muscles.  That  is,  these  mus- 
cles can  be  controlled  by  the  will.  For  example, 
we  can  control  the  motions  of  the  arm  or  leg.  It 
seems  that  the  impulses  which  cause  voluntary  mo- 
tions go  from  the  cerebrum  of  the  brain.  They  go 
from  the  "  gray  matter  ";  that  is,  the  nerve  cells  in  the 
surface  of  the  convolutions  of  the  cerebrum.  Also 
when  we  see  an  object,  hear  a  sound,  smell,  touch,  or 
taste  anything,  or  feel  pain,  impulses  come  from  the 
sense  organs  to  some  part  of  the  gray  matter  of  the 
cerebrum.  It  is  also  believed  that  when  we  remember 


INVOLUNTARY  ACTIONS  141 

anything,  know  anything,  or  feel  love,  hope,  fear, 
anger,  or  the  like,  it  is  some  part  of  the  cerebrum  that 
is  affected.  We  may  say  then  the  cerebrum  has  to  do 
with  sensations,  feelings,  all  mental  work,  and  all 
voluntary  acts. 

Involuntary  Actions.  —  Every  one  knows  that  a 
chicken  for  a  few  minutes  after  its  head  is  taken  of! 
will  jump  about  and  flap  its  wings  violently.  With- 
out its  head,  of  course,  it  has  no  brain.  The  part  of 
the  central  nervous  system  that  is  left  is  the  spinal 
cord.  There  is  no  longer  any  will  or  feeling  in  the 
animal,  yet  the  spinal  cord  is  able  to  make  the  mus- 
cles contract  in  jumping  and  flopping.  But  in  this 
case  it  has  been  proved  that  the  spinal  cord  will  not 
send  out  impulses  unless  impulses  come  to  it ;  that  is, 
unless  the  body  of  the  animal  touches  against  something. 
The  nerves  carry  an  impulse  to  the  cord  and  it  sends 
out  the  impulses  to  the  muscles.  This  is  an  action 
without  use  of  the  will.  It  is  called  reflex  action. 
There  are  many  such  actions.  A  few  examples  in 
the  human  body  will  illustrate  them.  If  an  object  is 
suddenly  thrust  in  front  of  the  eye,  it  will  cause  wink- 
ing. The  sight  of  the  object  makes  a  nervous  impulse 
that  goes  to  the  central  nervous  system;  this  sends  one 
out  to  muscles  that  move  the  eyelids.  This  will  all 
happen  before  we  have  time  to  think  or  will.  If  a 
finger  is  touched  with  a  hot  wire,  it  will  be  jerked  away 
by  the  spinal  cord  even  before  the  pain  is  felt.  Food 
in  the  mouth  will  cause  saliva  to  flow.  Food  in  the 
stomach  will  cause  secretion  of  gastric  juice.  A  crumb 
of  bread  in  the  larynx  will  produce  violent  coughing. 
Particles  of  dust  in  the  nose  will  cause  sneezing.  These 


142  CARE    OF   THE  NERVOUS  SYSTEM 

actions,  as  we  know,  are  not  caused  by  the  will,  but  are 
reflex  actions. 

Uses  of  Reflex  Actions.  —  It  is  easy  to  understand 
the  importance  of  having  parts  of  the  nervous  system 
which  will  act  in  this  way.  This  was  discussed  in  con- 
nection with  the  study  of  muscles.  The  eye  is  better 
protected  if  it  has  machinery  to  make  it  work  quickly, 
even  before  we  take  the  time  to  think  and  act.  So 
for  many  acts.  Perhaps  we  never  could  learn  just 
how  much  of  the  different  secretions  ought  to  be  made 
and  when  they  should  begin.  We  surely  could  not 
regulate  the  heart  beat  and  the  breathing  motions  just 
as  they  should  be  at  every  moment,  nor  could  we  keep 
them  going  every  minute  of  our  lives.  Thus  a  very 
great  part  of  the  necessary  actions  of  the  body  go  on 
perfectly  by  reflex  action,  in  little  children  as  well  as  in 
adults,  without  their  having  to  give  even  a  thought  to 
them. 

CARE  OF  THE  NERVOUS  SYSTEM 

We  have  seen  that  the  nervous  system  is  the  most 
important  of  all  the  organs  or  systems  of  the  body. 
Its  duty  is  the  most  complex.  It  manages  the  action 
of  every  organ  so  that  each  works  when  it  should  and 
ceases  at  the  right  time.  Through  it  all  our  acts  are 
guided.  On  its  working  just  right  depends  our  proper 
conduct  at  every  moment,  and  the  proper  action  of 
each  part  of  the  body.  With  these  facts  before  us, 
it  is  plain  why  the  care  of  the  nervous  system  is  of  the 
utmost  importance. 

The  nervous  system,  even  more  than  other  parts  of 


CARE    OF   THE  NERVOUS  SYSTEM  143 

the  body,  is  quickly  affected  by  the  character  of  the  air 
breathed,  and  by  the  quality  and  quantity  of  jood.  It 
is  affected  also  by  the  poisons  which  may  be  retained 
in  the  body  by  failure  to  have  them  discharged  by  the 
excretory  organs.  Consequently  all  of  these  matters 
must  be  attended  to  well  to  secure  a  healthy  working 
of  the  nervous  system. 

Sleep  has  for  its  special  function  restoration  of  the 
nervous  system  when  it  is  fatigued.  Of  course,  the 
muscles  also  gain  a  needed  rest  during  sleep,  but  sleep 
seems  to  be  especially  necessary  for  the  brain  and 
spinal  cord.  It  is  generally  thought  that  about  eight 
hours  of  the  twenty-four  should  be  spent  by  adults 
in  sleep.  Children  as  a  rule  should  have  more,  and 
very  young  children  much  more.  Adults  vary  a 
good  deal  in  the  amount  of  sleep  required,  accord- 
ing to  the  individual  disposition  and  employment. 
People  may  accustom  themselves  to  do  without  the 
proper  amount  of  sleep  for  a  while,  but  lack  of  sleep 
is  a  dangerous  state  and  is  sure  to  bring  bad  re- 
sults. A  clear  mind  and  a  healthy  body  demand 
regular  hours  of  sleep  and  enough  of  them.  People 
should  take  greater  care  to  keep  their  sleeping  time 
correct  than  to  preserve  their  property,  as  it  is  of  the 
greater  value.  Overwork,  worry,  with  lack  of  sleep,  are 
great  enemies  to  the  nervous  system.  Therefore  we 
repeat  that  plenty  of  good  jood,  pure  air,  out-oj-door 
exercise,  and  sufficient  sleep  are  necessary  to  keep  the 
nervous  system  in  good  working  order.  These  will 
prevent  nervous  troubles,  and  will  in  many  cases  be 
sufficient  to  restore  health  where  nervous  troubles 
exist.  Whatever  else  may  be  necessary  to  effect  a 


144  CARE    OF   THE   NERVOUS  SYSTEM 

cure  in  more  serious  cases,  these  conditions  are  es- 
sential. 

The  Nervous  System  and  Education.  —  A  habit  is  a 
way  of  doing  a  thing  or  a  way  of  thinking  which  has 
been  repeated  so  often  that  it  has  become  the  easiest 
way.  The  forming  of  a  habit  is  accomplished  by 
drilling  the  nervous  system  in  a  particular  way  of 
doing.  The  daily  life  of  an  adult  is  largely  the  carry- 
ing out  of  habits  which  have  been  formed.  When 
we  consider  that  a  well-fixed  habit  means  a  certain 
growth  of  the  nervous  system,  we  can  understand  how 
it  is  that  a  habit  is  so  hard  to  change.  We  speak  of 
good  habits  and  bad  habits.  They  are  ways  of  doing 
and  thinking  which  are  to  our  advantage  or  disad- 
vantage, or  which  make  us  pleasant  or  unpleasant 
companions.  Our  education  consists  very  largely  of 
forming  habits. 

The  fact  that  to  form  a  habit  requires  frequent  re- 
petition of  the  same  act  teaches  us  the  necessity  of  doing 
carefully  and  frequently  that  which  we  wish  to  be  part 
of  our  conduct,  and  to  refrain  from  repeating  those 
acts  which  we  do  not  wish  to  be  a  part  of  our  lives. 
To  do  away  with  a  bad  habit  which  has  been  acquired, 
it  is  necessary  to  watch  carefully  not  to  use  it  at  all, 
so  that  the  nervous  system  may  lose  the  power  to  per- 
form the  habit  easily.  This  is  very  hard  to  do  some- 
times, so  it  is  of  great  importance  that  the  habit  should 
not  be  formed.  Habits  are  most  easily  formed  and 
changed  in  youth,  while  the  nervous  system  is  growing. 
In  adult  life,  when  the  nervous  system  is  more  fixed 
in  structure  and  form,  habits  are  more  difficult  to 
form  or  change.  These  facts  have  long  been  known. 


EFFECT   OF  ALCOHOL    UPON  NERVOUS  SYSTEM     145 

Such  old  sayings  as,  "  As  the  twig  is  bent  the  tree  is 
inclined,"  "  You  can't  teach  an  old  dog  new  tricks," 
express  this  feeling.  The  subject  is  mentioned  here 
to  emphasize  the  fact  that  habits  are  really  connected 
with  certain  changes  in  the  body  itself,  and  should, 
therefore,  be  seriously  considered  in  their  formation. 

The  Effect  of  Alcohol  on  the  Nervous  System.  —  (For 
a  fuller  discussion  of  effects  of  alcohol,  see  Chapter 
XX.)  There  is  no  part  of  the  body  on  which  alcohol  has 
so  marked  an  effect  as  on  the  nervous  system.  When 
taken  into  the  stomach  it  is  soon  absorbed  and  circu- 
lated through  the  body,  and  its  effect  on  the  central 
nervous  system  (brain  and  spinal  cord)  is  immediate. 
Even  a  small  amount  of  alcohol  disturbs  the  action 
of  the  brain.  This  is  seen  in  the  false  judgments 
directly  following  its  use.  The  person  may  feel  warmer 
when  it  can  be  shown  that  he  really  is  no  warmer. 
He  says  the  drink  has  produced  an  exhilarating  effect 
on  him.  This  simply  shows  that  the  alcohol  has  so 
affected  his  brain  that  he  cannot  judge  correctly  even 
about  his  own  bodily  state. 

In  the  next  stage  he  gets  very  happy  or  angry  about 
almost  nothing,  or  he  becomes  silly  where,  in  his 
normal  state,  he  would  be  much  in  earnest.  All 
these  feelings  are  the  result  of  a  disordered  condition 
of  his  nervous  system.  He  is  deceived,  and  he  can  not 
adapt  himself  to  his  conditions.  If  he  should  be  in 
such  a  state  for  a  considerable  time,  he  could  not  escape 
making  great  mistakes  in  his  conduct.  A  man  thus 
deliberately  makes  himself  a  less  intelligent  being. 
He  disturbs  those  functions  which  we  regard  as  the 
highest,  and  which  we  are  accustomed  to  look  upon 

IND.    PR.    PHYS.  —  IO 


146  CARE    OF   THE  NERVOUS  SYSTEM 

with  pride  as  the  chief  characteristics  by  which  we 
are  distinguished  from  the  lower  animals. 

If  greater  amounts  of  alcohol  are  used,  all  these 
symptoms  are  intensified  until  there  may  be  a  com- 
plete overthrow  of  the  reason  and  a  loss  of  voluntary 
control  over  the  body.  The  sense  impressions  may 
be  wholly  misinterpreted.  Such  excessive  use  of 
alcohol,  if  long  continued,  will  so  profoundly  disturb 
the  action  of  the  brain,  that  the  patient  may  be  at- 
tacked with  such  diseases  as  delirium  tremens  or 
insanity,  whose  final  outcome,  after  much  misery,  is 
death. 

The  moderate  but  long-continued  use  of  alcohol 
has  not  the  same  effect  on  all  people.  In  some  it 
may  cause  little  apparent  injury,  while  in  others  it 
will  in  time  produce  changes  in  the  structure  of  the 
brain.  These  changes  are  similar  in  character  to 
those  which  occur  in  the  kidneys,  the  liver,  and  the 
heart;  that  is,  there  is  a  greater  development  of  the 
connective  tissues  at  the  expense  of  the  nervous  ele- 
ments of  the  brain.  The  effect,  however,  is  more 
injurious  on  the  body,  as  a  whole,  when  the  central 
nervous  system  becomes  deranged,  for  through  it  all 
the  other  organs  are  more  seriously  affected. 


CHAPTER    XVI 
SENSATIONS 

Definition.  —  By  the  term  " sensations"  is  meant  the 
impressions  or  feelings  which  are  made  upon  our 
minds  by  the  things  outside  of  our  bodies,  or  by 
changes  within  our  bodies.  For  example,  a  bright 
light  gives  us  one  kind  of  an  impression,  a  vibrating 
tuning-fork  another,  an  odor  still  another.  Or,  we 
may  have  sensations  from  changes  within  the  body, 
as  a  feeling  of  thirst  or  of  fatigue. 

It  is  through  parts  of  the  body  which  give  us  these 
impressions  or  feelings  that  we  gain  our  knowledge  of 
things  outside  of  us,  or  of  the  state  of  our  own  bodies. 

Special  and  General  Sensations.  —  If  one  con- 
siders the  various  sensations  he  has,  and  will  com- 
pare them,  he  will  see  that  they  differ  very  much  in 
the  definiteness  with  which  they  can  be  located  in 
the  body.  When  one  feels  tired,  it  is  hard  to  say 
just  where  the  feeling  is  located.  Even  after  one  has 
become  tired  from  continued  action  of  the  arms,  the 
feeling  of  fatigue  can  not  be  located  in  any  particular 
part  of  the  arms,  nor  does  it  seem  to  be  confined  to 
the  arms  alone. 

It  is  very  different  when  we  receive  a  sensation  from 
an  object  touching  the  finger.  In  this  case  it  can  be 


148  SENSATIONS 

determined  just  where  the  point  is  that  is  touched,  and 
the  idea  gained  by  the  sensation  is  more  definite  and 
distinct. 

Sensations  like  the  latter  are  called  special  sensa- 
tions, while  those  like  fatigue  are  known  as  general 
sensations. 

Sense  Organs.  — The  special  sensations  are  those 
of  sight,  hearing,  smell,  taste,  touch,  and  temperature. 
Each  of  these  has  a  special  kind  of  apparatus  with 
which  the  sensation  is  produced.  In  each  case  it 
consists  of,  first,  an  outer  part  which  is  .  so  formed 
that  it  can  be  affected  by  some  peculiar  kind  of  energy, 
the  perception  of  which  energy,  as  something  differ- 
ent from  any  thing  else,  leads  us  to  call  the  organ 
a  special- sense  organ ;  second,  the  sensory  nerve  ;  and 
third,  the  nerve  center  in  the  brain. 

General  Sensations.  —  In  the  production  of  gen- 
eral sensations  there  are  also  the  inner  parts,  the 
nerve  centers,  and  the  sensory  nerves,  and  there  may 
be  special  outer  nerve  endings.  But  how  they  ap- 
pear and  where  they  are  located  is  not  known.  The 
general  sensations  are  numerous,  and  many  of  them 
hard  even  to  describe.  Among  them  are  pain,  hunger, 
thirst,  nausea,  and  fatigue. 

Pain.  —  Any  one  of  the  sensory  nerves,  whether  of 
the  special  or  general  sensations,  seems  to  be  able  to 
give  rise  to  the  sensation  of  pain  if  stimulated  with 
too  great  energy.  Thus,  light,  sound,  things  that 
touch  the  skin,  or  that  affect  the  nerves  connected  with 
any  part  of  the  body,  —  in  fact,  which  either  give  rise 
to  a  pleasurable  sensation  or  to  no  feeling  at  all,  and 
thus  are  known  .only  by  the  reflex  actions  which  they 


THE   SENSE   OF   TOUCH  149 

produce,  —  may  cause  intense  pain  if  the  stimulus  is 
increased  beyond  a  certain  degree. 

The  Use  of  Pain.  —  A  means  of  producing  pain  is 
of  the  greatest  importance  to  the  body.  It  is  simply 
the  way  in  which  the  nervous  system  calls  attention 
in  the  most  emphatic  manner  to  the  fact  that  some- 
thing is  wrong. 

Pain  even  does  more  than  call  attention  to  the 
wrong.  It  drives  us  to  right  the  wrong,  to  get  rid  of 
the  pain.  We  are  sometimes  rather  slow  to  do  what 
is  right,  even  when  our  attention  is  called  to  it.  We 
must  have  a  stronger  stimulus  to  action.  Pain  fur- 
nishes us  that  stimulus.  Pain  is  graded  all  the  way 
from  simply  being  an  unpleasant  feeling  up  to  the 
most  intense  suffering.  To  avoid  the  latter  it  is  cer- 
tainly well  to  pay  attention  to  the  former. 

Hunger  and  thirst  are  forms  of  sensations  which 
arise  from  a  diminished  supply  of  food  and  water  to 
the  tissues.  They  are  produced  through  parts  of  the 
nervous  system  not  definitely  known.  These,  to- 
gether with  the  feeling  of  having  had  enough  when 
sufficient  food  and  drink  have  been  taken,  are  of  the 
utmost  importance  in  regulating  the  supply  of  both. 

Above  all,  we  should  attempt  to  preserve  the  healthy 
action  of  these  sensations,  since,  when  they  are  not 
abused  or  abnormally  developed,  they  furnish  us 
with  the  very  best  guides  in  the  extremely  important 
process  of  taking  food  and  drink.  With  these  dis- 
turbed, the  preservation  of  the  general  health  is  almost 
impossible. 

The  Sense  of  Touch.  —  This  sensation  is  produced 
by  pressure  on  the  epidermis,,  also  on  the  mucous 


I  50  SENS  A  TIONS 

lining  of  the  mouth  and  in  the  beginning  of  the  nasal 
passages.  The  special  organs  of  touch  are  micro- 
scopic bodies  of  a  peculiar  form  placed  in  the  papillae, 
or  just  underneath  the  epidermis.  The  nerves  of 
touch  end  in  these  bodies,  and  when  pressure  is  brought 
to  bear  on  the  epidermis  it  starts  impulses  in  the  nerves, 
which,  coming  to  the  brain,  give  the  sensation  of 
touch. 

These  organs  are  unequally  distributed  in  different 
parts  of  the  skin,  being  much  greater  in  number  in 
the  palms  of  the  hands,  the  lips  and  tongue,  and  in 
the  soles  of  the  feet,  than  in  other  parts  of  the  body. 
The  little  hairs  scattered  over  the  body,  which  have  at 
their  roots  branches  of  sensory  nerves,  greatly  aid  in 
determining  the  pressure  of  anything  against  the  skin. 

Different  parts  of  the  skin  differ  very  much  in  the 
accuracy  with  which  they  report  about  the  things 
touched.  It  is  only  by  the  palms  of  the  hands,  bot- 
toms of-  the  feet  and  toes,  tip's  of  the  fingers,  and  by 
the  lips  and  tongue  that  the  shapes  of  things  can  be 
made  out  when  touch  alone  is  used. 

Other  parts  of  the  body,  such  as  the  skin  on  the 
forehead,  can  determine  the  presence  of  a  lesser  pres- 
sure than  can  the  fingers  and  the  palms  of  the  hands. 
It  would  be  profitable  for  the  pupil  to  experiment 
in  these  particulars  with  different  parts  of  the  sur- 
face of  the  body. 

The  Sense  of  Temperature.  — This  is  the  sense 
by  which  we  determine  the  differences  of  the  tem- 
perature of  objects.  Its  outer  organs  are  in  the  skin, 
in  the  lining  of  the  mouth,  pharynx,  and  esophagus. 
These  outer  parts  of  the  sense  organ  of  temperature 


THE   SENSE    OF    TASTE  151 

are  mingled  in  many  places  with  those  of  touch,  but 
the  two  have  been  clearly  proved  to  be  distinct  sen- 
sations and  must  have  different  nerves. 

One  may,  by  employing  a  warm  or  a  cold  rod,  ex- 
plore the  surface  of  the  skin  and  determine  what  parts 
are  most  and  what  parts  least  sensitive  to  heat  and  cold. 

The  uses  of  the  senses  of  touch  and  temperature 
are  very  obvious.  We  may  say  for  them  that  they 
are  not  the  least  important  of  the  senses.  The  sense 
of  touch  seems  to  be  possessed  to  a  greater  or  less 
degree  of  definiteness  by  all  animals. 

The  Sense  of  Taste.  —  The  nerves  of  taste  end 
in  little  bodies  in  the  mucous  covering  of  the  tongue 
and  in  the  soft  palate.  This  sense  determines  cer- 
tain properties  of  liquids.  The  forms  of  the  sensa- 
tion of  taste  have  been  stated  to  be  included  in  the 
four  following:  bitter,  sweet,  saline,  and  sour. 

The  little  bodies  in  which  the  nerves  of  taste  end 
are  placed  in  some  of  the  papillae  in  the  parts  named, 
and  are  only  affected  when  the  substances  are  dis- 
solved. In  this  the  saliva  is  of  great  aid. 

We  are  accustomed  to  think  that  we  taste  many 
things  which  we  know  only  by  the  sense  of  smell. 
This  is  the  case  with  flavors,  like  that  of  vanilla,  of 
onion,  of  garlic,  and  with  the  flavors  of  different  kinds 
of  meats. 

Our  opinion  in  this  regard  is  only  an  example  of 
how  we  often  make  use  of  things  a  long  time  with- 
out stopping  to  determine  accurately  anything  about 
them.  By  carefully  keeping  the  odors  of  such  sub- 
stances that  have  flavors  out  of  the  nostrils  their  so- 
called  flavors  can  not  be  tasted. 


152  SENSATIONS 

The  Sense  of  Smell.  — The  fibers  of  the  nerve  of 
smell  end  in  little  cells  embedded  in  the  mucous  mem- 
brane of  the  higher  parts  of  the  nasal  passages.  These 
cells  come  to  the  very  surface,  where  their  extremities 
are  kept  moist  by  mucus.  They  are  affected  by 
vapors  and  gases. 

A  very  great  number  of  odors  can  be  distinguished 
by  the  organ  of  smell.  Its  sensitiveness  is  remark- 
able when  it  is  considered  what  small  quantities  of 
substances  can  fill  a  large  room  with  odors  which 
can  be  detected  by  the  sense  of  smell,  although  but 
a  very  small  part  of  the  air  containing  the  odor  can 
reach  the  olfactory  surface  of  the  nose. 

The  Uses  of  Taste  and  Smell. —The  chief  uses 
of  these  senses  are  plainly  to  examine  both  the  food 
taken  and  the  air  breathed,  and  both  organs  are  lo- 
cated admirably  for  these  purposes. 


CHAPTER   XVII 

SIGHT   AND   HEARING 

External  Parts  of  the  Eye.  —  We  may  begin  our 
study  of  the  eye  by  observing  what  is  exposed  to  view 
in  our  own  or  in  our  companion's  eye.  First  we 
have  the  curtain,  the  eyelids,  fringed  by  the  eyelashes. 
Just  back  of  the  eyelids  is  the  front  part  of  the  ball 
of  the  eye. 

This  looks  like  glass.  Its  shining  appearance  is 
due  to  its  being  very  smooth  and  continually  washed 
over  by  the  secretion  of  tears.  This  secretion  is  rubbed 
over  the  eye  by  the  act  of  winking,  which  is  kept  up 
incessantly. 

As  the  tears  pass  over  the  eye  they  flow  away  and 
are  gathered  up  by  two  tiny  openings  in  the  inner 
corner  of  the  eye.  These  openings  lead  to  the  tear 
ducts  (lachrymal  ducts).  The  ducts,  after  passing 
through  the  lachrymal  bones,  empty  upon  the  inner 
surface  of  the  nostrils. 

The  very  front  of  the  eyeball  is  transparent,  and 
when  viewed  from  one  side  is  seen  to  protrude  slightly 
from  the  rest  of  the  surface.  This  is  the  cornea. 
Beyond  the  edges  of  the  cornea  comes  the  white  of 
the  eye. 

Looking  through  the  cornea,  we  see  the  colored 
'53 


154  SIGHT  AND  HEARING 

part,  called  the  iris.  It  has  a  round  black  spot  in  the 
center  known  as  the  pupil. 

The  pupil  is  only  a  round  hole  in  the  iris.  It  is 
black,  as  is  a  hole  in  any  closed  box,  because  there 
is  very  little  light  inside  to  come  out. 

Fitting  closely  over  the  visible  front  part  of  the 
eyeball  is  a  very  thin  layer  of  skin  called  conjunc- 
tiva. It  runs  from  the  eyeball  to  the  under  side  of 
the  lids,  at  whose  edges  it  becomes  continuous  with 
the  skin  of  the  outer  surface  .of  the  lid. 

The  conjunctiva  is  well  supplied  with  nerves,  which 

give  a  sensation  of  great  pain  on  the  presence  of  any 

foreign  body  on  the  surface  of  the  eye  or  under  the  lid. 

The  Eyeball.  — The  ball  of  the  eye  is  a  globe  about 

one    inch   in    diameter.     It    rests   in    a   bony  socket, 

in  which  it  can  be 
turned  in  every  direc- 
tion by  its  muscles. 
Between  the  eyeball 
and  the  walls  of  the 
socket  is  a  padding, 
principally  of  fat  and 
connective  tissue.  The 

THE  EYEBALL  WITH  ITS  MUSCLES.  .       ,     ,  ,  , 

eye  is   held   in   place 

very  firmly,  as  one  will  find  when  he  attempts  to  re- 
move the  eyeball  from  the  head  of  some  animal  for 
study. 

Fig.  57  shows  the  eyeball  with  its  muscles  attached. 
The  upper  muscle  not  attached  to  the  ball  belongs  to 
the  upper  eyelid.  The  muscle  in  front  is  cut  away 
to  show  the  optic  nerve  at  2  just  back  of  it.  The 
ball  and  optic  nerve  are  also  shown  in  Fig.  58. 


THE    WALLS   OF   THE  EYE 


155 


The  Walls  of  the  Eye.  — The  eye  may  be  con- 
sidered as  a  globular  box.  The  outer  walls  consist 
of  three  layers  or  coats.  Fig.  58  is  a  section  of  an 
eye  which  well  shows  these  parts.  The  front  part 
consists  of  the  transparent  cornea,  continuing  as  the 


Cm, 


Fig.  58. 

SECTION  OF  THE  EYEBALL. 

COM,  conjunctiva;  C,  cornea;  A,  aqueous  humor;  /,  iris;  L,  crystalline  lens; 
V,  vitreous  humor;  Sc,  sclerotic  coat;  Ch,  choroid  coat;  R,  retina;  O,  optic  nerve; 
Cut,  ciliary  muscle;  Sh,  sheath  of  optic  nerve. 

white  of  the  eye,  which  is  called  the  sclerotic  coat  (Sc). 
This  at  the  back  extends  over  the  optic  nerve  as  its 
sheath. 

This  covering  is  of  very  tough  connective  tissue, 
and  is  the  main  part  of  the  wall  of  the  box,  support- 
ing the  other  parts  and  furnishing  places  for  the  at- 
tachment of  muscles,  as  seen  in  Fig.  57. 


156  SIGHT  AND   HEARING 

Just  inside  of  this  coat  lies  the  choroid  coat  (Ch 
in  Fig.  58).  It  is  dark  in  color  and  closely  filled 
with  blood  vessels.  Toward  the  front  part  of  the 
eye  it  contains  the  muscular  fibers  (Cm)  of  the  ciliary 
muscle.  Farther  forward  it  is  continued  into  the 
iris,  marked  (/).  Just  inside  the  choroid  is  the  very 
thin  transparent  retina  (R).  It  is  continuous  with 
the  optic  nerve  (O). 

The  walls  are  held  out  firmly  in  their  spherical 
shape  by  the  contents  of  the  globe,  which  are  the 
vitreous  humor  (V),  the  crystalline  lens  (L),  and  the 
aqueous  humor  (A).  The  vitreous  humor  looks  like 
a  very  transparent  jelly;  the  lens  is  firmer,  and  when 
fresh  has  the  appearance  of  a  clear  convex  lens  of 
glass;  while  the  aqueous  humor  consists  of  but  a  few 
drops  of  a  liquid  that  is  mostly  water.  The  lens  is  held 
in  place  by  a  sheath  of  a  kind  of  connective  tissue. 

Seeing.  —  As  was  stated  above,  it  is  a  part  of  the 
retina  that  is  affected  by  light.  It  is  that  part  which 
lies  against  the  choroid  coat.  The  retina,  although 
exceedingly  thin,  is  a  very  complex  structure.  While 
the  description  of  its  microscopic  parts  may  be  omitted, 
it  may  be  stated  that  the  fibers  of  the  optic  nerve  pass 
to  the  front  of  the  retina,  where  they  spread  over  the 
whole  retina.  The  end  of  each  fiber,  however,  turns 
toward  the  choroid  coat,  and,  through  different  parts 
of  the  retina,  becomes  connected  with  each  one  of  the 
vast  numbers  of  minute  bodies  in  the  retina  known 
as  the  rods  and -cones,  whose  ends  point  toward  the 
choroid  coat. 

The  light  affects  these  rods  and  cones,  and  they 
start  the  stimulus,  which,  traveling  along  the  optic 


ACCOMMODATION   OF  THE   EYE   TO   DISTANCES     157 

nerve  to  the  nerve  center  in  the  brain,  produces  the 
sensation. 

Distinct  Vision.  —  Perception  of  the  exact  out- 
lines of  an  object  can  only  occur  when  a  definite  image 
of  the  object  is  formed  on  the  rod  and  cone  layer 
of  the  retina.  Every  one  knows  that  an  image  of  a 
lamp  flame  or  of  the  window  can  be  formed  on  a 
sheet  of  white  paper  by  the  use  of  a  convex  lens. 

The  photographer  uses  a  convex  lens  also  to  form 
an  image  in  the  camera.  In  the  eye,  the  cornea  and 
the  crystalline  lens  are  the  convex  lenses  which  form 
the  image  on  the  rods  and  cones. 

The  iris,  by  narrowing  and  enlarging  the  pupil,  which 
actions  are  accomplished  by  muscular  fibers  in  its 
substance,  regulates  the  amount  of  light,  and  thus 
helps  to  make  the  image  more  distinct. 

Accommodation  of  the  Eye  to  Different  Distances.  - 
If,  while  you  keep  your  eyes  fixed  on  the  words  of  this 
page,  you  give  attention  to  some  object  beyond  the 
book,  the  farther  object  wi-11  be  found  to  be  indistinct. 
If  now  you  look  at  the  object  beyond,  the  words  of 
the  book  are  indistinct.  The  reason  for  this  is  that 
a  lens  can  not  make  on  a  screen  definite  images  of 
objects  at  different  distances  at  the  same  time.  If 
the  lenses  and  the  retina  of  the  eye  were  to  remain 
just  exactly  the  same  in  shape  and  distance  from  each 
other,  we  could  never  see  anything  in  definite  outline 
except  at  one  certain  definite  distance. 

The  eye  is  enabled  to  accommodate  itself  to  ob- 
jects at  different  distances  by  changing  the  amount 
of  curvature  of  the  crystalline  lens.  This  is  done  by 
the  action  of  the  ciliary  muscle  (Cm)  in  conjunction 


158  SIGHT  AND  HEARING 

with  other  parts.  The  lens  becomes  more  curved  for 
a  near  object  and  less  so  for  distant  objects;  that 
is,  objects  more  than  twenty  feet  away. 

Shortsightedness.  —  A  normal  eye  can  accom- 
modate itself,  as  has  just  been  shown,  to  both  near 
and  distant  objects.  In  a  nearsighted  e.ye,  generally 
on  account  of  the  too  great  length  of  the  eyeball, 
the  lens  can  not  make  the  image  of  distant  objects 
fall  on  the  rods  and  cones,  and  even  near  objects 
must  be  brought  close  to  the  eye  to  be  seen  clearly. 
Concave  glasses  will  correct  this  defect. 

In  Longsightedness  the  eyeball  is  commonly  too 
short,  and  thus  prevents  images  of  near  objects  from 
being  formed  at  the  proper  place.  Convex  glasses 
are  used  to  correct  this  defect. 

There  are  many  other  defects  which  eyes  may  pos- 
sess which  can  not  be  explained  here.  As  most  of 
them  are  such  in  nature  that  they  grow  worse  in  time 
and  may  prove  serious,  it  is  always  best,  when  any 
are  suspected,  to  have  the  eye  examined  by  an 
oculist. 

Sensation  of  Hearing.  —  An  object  producing  a 
sound,  such  as  a  violin  string,  does  so  by  vibrating 
very  rapidly;  that  is,  it  swings  backward  and  for- 
ward with  great  rapidity.  These  vibrations  give 
their  motions  to  the  wood  of  the  body  of  the  violin, 
and  this  in  turn  sets  the  air  to  vibrating.  Every 
little  particle  of  air  is  swinging  to  and  fro  with  the 
same  rate  as  the  vibrating  body. 

The  sensations  of  hearing  are  produced  by  these 
vibrations  being  transmitted  by  parts  of  the  hear- 
ing apparatus  to  the  little  bodies  in  the  innermost 


THE  AUDITORY  APPARATUS 


159 


part  of  the  ear,   in  which  the  auditory  nerve   fibers 
end. 

The  Auditory  Apparatus  is  very  complicated,  and 
our  description  will  include  but  a  brief  outline.  The 
apparatus  is  generally  con- 
sidered in  three  divisions: 
the  external  ear,  the  middle 
ear,  and  the  internal  ear. 

The  external  ear  includes 
the  visible  projections  called 
the  pinna,  and  the  tube  that 
leads  from  it,  known  as 
the  external  auditory  canal, 
which,  at  its  inner  end,  is 
closed  by  a  membrane 
called  the  membrana  tym- 


sc 


Fig.  59. 


THE    AUDITORY    APPARATUS   WITH   THE 
SURROUNDING  BONE  REMOVED. 

^/.external  auditory  canal;   SC,  semi- 
circular canals;   C,  cochlea. 


pani,    which    separates    it 
from  the  middle  ear. 

The  middle  ear  is  a  small 
cavity  in  the  temporal 
bone,  lined  by  a  thin  mucous  membrane.  It  opens 
into  the  pharynx  by  the  Eustachian  tube.  It  is  sepa- 
rated from  the  external  canal  by  the  membrana  tym- 
pani.  Three  small  bones,  the  malleus,  the  incus,  and 
the  stapes,  fastened  together  and  attached  to  the  sides 
of  the  cavity,  connect  the  membrana  tympani  with  a 
membrane  between  the  middle  and  the  internal  ear. 
The  middle  ear  contains  air,  which  comes  into  it  through 
the  Eustachian  tube. 

The  internal  ear  consists  of  very  small  tubes  of  mem- 
brane, which  lie  in  corresponding  tubes  of  bony  chan- 
nels in  the  temporal  bone.  Both  inside  and  outside 


i6o 


SIGHT  AND  HEARING 


sc 


of  these  tubes  of  membrane  is  a  liquid  which  is  mainly 
water.  The  three  divisions  of  the  internal  ear  are  the 
semicircular  canals,  the  vestibule,  and  the  cochlea. 

The  auditory  nerve 
fibers  end  in  cells 
on  certain  parts  of 
the  internal  lining 
of  these  membra- 
nous tubes. 

The  functions  of 
some  of  these  parts 
are   not   definitely 
F'9-  60-  known,    but    it    is 

A  DIAGRAM  OF  A  SECTION  OF  THE  AUDITORY          believed     that     the 

E,  external  canal;  M,  in  the  middle  ear,  where  is     Sensation  of   SOUnd 
the  chain. of  bones;    I',  vestibule;    SC,  semicircular     •  i  i    i         ,1 

canals;  N,  auditory  nerve;   C,  cochlea;  ET,  Eusta-     IS  produced   by  the 

stimuli  to  the  nerve 

endings  in  the  internal  parts  of  the  cochlea.  The 
cochlea  consists  of  three  tubes  wound  around  in  the 
shape  of  a  snail  shell.  The  nerve  fibers  end  in  the 
walls  of  the  middle  tube. 

General  View  of  the  Action  of  the  Auditory  Appa- 
ratus. —  The  motions  of  the  vibrating  body  set  the 
air  into  vibrations;  the  vibrating  air  causes  the  mem- 
brana  tympani  to  swing  to  and  fro  with  the  same 
rate;  these  swings  are  communicated  by  the  series 
of  bones  to  the  membrane  to  which  the  stapes  is  at- 
tached. The  motions  of  this  membrane  set  the  liquid 
of  the  internal  ear  in  motion,  and  this  acts  on  parts 
that  set  in  motion  the  bodies  in  which  the  auditory 
fibers  end.  The  motions  start  this  stimulus,  which 
causes  the  sensation  of  hearing. 


CHAPTER  XVIII 

CARE  OF  THE  EYE  AND  EAR 

CARE  OF  THE  EYE 

THE  eyes  are  such  extremely  useful  organs,  and  at 
the  same  .time  so  delicate,  that  they  call  for  special 
care  to  shield  them  from  harm.  It  is  especially  neces- 
sary to  guard  against  injuries  from  the  outside,  wrong 
use  of  the  eyes,  and  contagious  diseases  of  the  eyes. 

We  have  seen  that  the  eyes  are  naturally  well  pro- 
tected by  being  placed  in  bony  sockets  with  slightly 
projecting  rims,  so  that  blows  or  sources  of  injury, 
except  from  directly  in  front,  do  not  have  much  chance 
of  injuring  them,  and  the  eyelids  offer  quite  a  protec- 
tion for  those  coming  from  that  direction.  The  large 
objects  which  might  make  severe  wounds  we  are  usu- 
ally careful  to  look  out  for.  Children,  however,  may 
sometimes  carelessly  play  with  such  toys  as  bow  and 
arrows  or  pea  shooters  and  endanger  their  playmates' 
eyes.  Small  things  which  we  can  not  so  well  control, 
such  as  flying  insects,  cinders,  or  other  particles  carried 
by  the  wind,  or  minute  pieces  of  steel  thrown  off  in 
working  with  machinery,  may  be  the  cause  of  much  pain 
or  even  of  permanent  injury.  Of  course  these  should 
be  removed  without  delay.  The  pain  usually  drives 
us  to  get  them  out  as  soon  as  possible.  Fortunately, 
most  of  these  things  can  be  easily  removed,  if  they 

IND.    PR.' PHYS. —  II  l6l 


1 62  CARE    OF   THE  EYE  AND  EAR 

have  not  become  embedded  in  the  eye.  By  drawing 
out  the  eyelids  and  having  the  eyeball  turned  in  dif- 
ferent directions  a  good  part  of  its  surface  and  the 
inner  surface  of  the  lids  can  be  examined.  It  will 
be  remembered  that  the  conjunctiva,  that  is,  the  mem- 
brane which  covers  the  inside  surface  of  the  lids,  and 
the  part  of  the  eyeball  covered  by  them,  will  not  per- 
mit objects  to  get  behind  the  eyeball  without  piercing 
that  membrane.  Thus  by  examining  carefully  all  its 
surface  these  small  objects  may  usually  be  found  and 
removed. 

The  inner  surface  of  the  upper  lid  is  more  difficult 
to  examine,  as  it  can  not  be  so  easily  turned  back  as 
the  lower.  There  is  in  it  a  plate  of  cartilage  which 
makes  it  more  firm.  With  a  little  skill,  however,  it 
can  be  turned  inside  out.  Take  hold  of  the  eyelashes 
with  one  hand  and  draw  out  the  edge  of  the  lid.  At 
the  same  time, with  some  smooth,  slender  object,  like  a 
lead  pencil,  press  on  the  middle  of  the  outside  surface 
of  the  lid  while  the  edge  of  the  lid  is  drawn  upward.  If 
properly  managed,  the  firm  cartilage  in  the  lid  is  turned 
upside  down  and  brings  the  inner  surface  of  the  lid  out- 
side so  that  it  can  be  examined.  The  offending  body  can 
then  be  removed  by  a  clean  silk  or  linen  handkerchief 
folded  to  a  point  over  a  lead  pencil  or  toothpick.  If 
the  foreign  body  has  been  embedded  in  the  eyeball, 
great  care  should  be  taken  in  removing  it.  Such  an 
operation  ought  to  be  intrusted  only  to  a  skilled  phy- 
sician or  to  an  oculist. 

If  any  chemical  substance  should  chance  to  be  thrown 
into  the  eye,  it  should  be  washed  out  immediately  with 
abundant  clean  water;  if  the  substance  is  alkaline,  like 


CARE    OF   THE   EYE  163 

lye  or  lime,  a  little  vinegar  could  be  added  to  the  water;  if 
it  is  an  acid  substance,  a  soap  solution  could  be  used,  but 
all  must  be  finally  removed  with  clean  water.  The  most 
common  of  such  substances  to  get  into  people's  eyes  is 
lime,  since  it  is  used  in  making  whitewash  and  mortar 
and  plaster.  A  bit  of  one  of  these  substances  in  the 
eye  is  very  painful  and  dangerous,  and  should  be  washed 
out  immediately.  Any  one  engaged  in  an  occupation 
which  exposes  the  eyes  to  flying  particles,  such  as  grind- 
ing or  polishing  metals  or  glass,  should  wear  some- 
thing over  the  eyes  to  protect  them. 

Quite  different  kinds  of  injuries  come  from  the 
wrong  use  of  the  eyes.  If  the  eyes  are  good,  that  is, 
if  they  see  distinctly,  —  are  not  nearsighted  or  farsighted, 
—  they  may  be  injured  by  habits  of  using  them  on  fine 
work  or  in  a  poor  light.  If  the  light  is  poor,  we  are 
likely  to  strain  the  eyes  unconsciously,  by  trying  to  focus 
them  so  as  to  bring  out  more  clearly  the  objects  we 
are  looking  at.  The  straining  at  focusing  will  do  no 
good  if  the  light  is  not  there,  and  the  continued  strain- 
ing of  the  eyes  is  sure  to  change  them  permanently  so 
that  they  are  no  longer  normal.  They  become  weak 
or  nearsighted  or  astigmatic.  Besides  injuring  the 
eyes,  the  "  eye  strain  "  may  become  through  its  peculiar 
reflex  connections  the  cause  of  very  many  other  severe 
troubles  not  apparently  connected  with  seeing.  Some 
of  these  are  headaches,  dizziness,  fainting,  dyspepsia, 
and  other  intestinal  troubles.  Often  people  have  suf- 
fered with  quite  severe  bodily  troubles  and  have  been 
treated  for  these  without  relief,  when  finally  proper 
treatment  of  the  eyes,  so  as  to  do  away  with  eye  strain, 
has  completely  'cured  them  of  the  trouble. 


164  CARE    OF   THE  EYE  AND  EAR 

The  book  or  work  should  be  in  a  good  light  and 
near  enough  to  be  seen  with  perfect  comfort.  It  is 
best  that  the  light  come  in  from  the  left.  When  the 
light  comes  from  the  back  or  right,  shadows  of  the 
head  or  hands  fall  across  the  work  and  annoy  one, 
and  when  from  the  front,  it  pours  directly  into  the 
eyes  as  well  as  on  the  work,  and  tires  the  eyes  very 
much.  These  uncomfortable  positions  or  a  poor 
light  may  be  endured  by  good  eyes  for  a  short  time, 
but  continuous  exposure^  to  them  will  surely  affect 
the  eyes  injuriously Jn  time. 

If  the  eyes  are  not  normal, — that  is,  if  they  are  weak, 
astigmatic,  nearsighted  or  f  arsighted,  —  then  they  are  con- 
stantly being  put  to  a  strain  in  any  reading  or  fine  work, 
and  any  of  the  many  troubles  which  go  with  eye  strain 
may  result,  while  the  eyes  themselves  grow  constantly 
worse.  When  any  trouble  of  this  kind  is  present,  the 
eyes  should  be  examined  by  a  competent  oculist,  who 
will  with  his  instruments  determine  the  trouble  and 
prescribe  the  glasses  necessary  to  be  worn.  His  advice 
should  be  carefully  followed.  Sometimes  the  muscles 
of  the  eyes  do  not  work  properly,  so  that  both  eyes  are 
not  accurately  turned  on  the  object  examined  at  the 
same  time,  that  is,  one  eye  may  be  turned  in  too  much, 
"  cross-eye,"  or  turned  out  too  much,  "  wall  eye,"  or 
too  much  in  some  other  direction.  For  these  troubles 
only  those  trained  in  the  treatment  of  the  eye  should  be 
employed. 

There  is  a  great  number  of  diseases  which  may  affect 
the  eyes,  and  when  any  of  them  appears,  the  advice  of  a 
physician  or  oculist  should  be  sought  as  to  the  remedies 
to  be  applied.  Avoid  using  any  kind  of  "  eye  wash," 


CARE    OF   THE  EYE  165 

lotion,  or  other  remedy  advised  by  any  other  person. 
The  edges  of  the  lids,  as  also  the  lids  themselves  and  the 
rest  of  the  face,  should  be  kept  clean  by  washing  with 
water  or  soap  and  water.  The  surface  of  the  healthy 
eye  does  not  need  any  other  cleansing  than  the  means  na- 
ture has  provided,  that  is,  the  tears  and  winking.  Even 
clean  water  continuously  applied  would  cause  injury. 

There  are  some  diseases  of  the  eyes  which  are  very 
contagious.  As  there  is  special  danger  of  communica- 
tion by  means  of  a  common  towel,  the  one  with  the 
"  sore  eyes  "  should  have  a  towel  and  basin  to  himself, 
and  care  should  be  taken  that  he  use  no  other.  The 
term  "  sore  eyes  "  is  applied  to  several  different  diseases 
of  the  eyes,  some  of  which  are  and  others  are  not 
contagious  or  very  dangerous.  The  physician  should 
be  consulted  in  every  case,  and  if  the  disease  is  conta- 
gious or  dangerous,  his  directions  for  the  treatment,  and 
for  the  protection  of  others  from  the  contagion,  should 
be  strictly  followed.  Carelessness  in  this  regard  has 
sometimes  allowed  one  person  to  be  the  cause  of  injury 
and  even  blindness  in  many  others. 

To  sum  up:  Be  careful  to  have  a  good  light  on  read- 
ing or  work,  preferably  from  the  left  or  from  above. 
Have  the  work  in  a  convenient  position  so  that  there 
will  be  no  strain  of  eyes  or  other  parts  of  body  to  see 
it  distinctly.  If  working  where  there  are  flying  parti- 
cles, wear  a  protective  covering  for  the  eyes.  If  there 
is  any  indication  of  nearsightedness,  farsightedness, 
or  any  question  of  weakness  of  the  eyes,  have  them 
examined  for  the  proper  glasses;  if  any  disease  of  the 
eyes  appears,  have  them  examined  promptly,  and  be 
faithful  in  following  the  treatment  prescribed. 


1 66  CARE   OF  THE  EAR 


CARE  OF  THE  EAR 

Foreign  bodies  may  get  into  the  external  canal  of 
the  ear.  The  greatest  care  should  be  taken  in  attempt- 
ing to  remove  them.  For,  as  we  have  just  seen,  the 
canal  is  only  about  one  inch  long,  and  at  its  end  is  the 
delicate  membrane  of  the  drum  of  the  ear,  which  would 
be  injured  very  readily  by  the  instrument  used.  It  is 
best  to  attempt  first  to  remove  the  object  by  washing 
it  out  with  a  stream  of  warm  water  sent  gently  into 
the  ear  by  means  of  a  syringe.  The  small  nozzle  of 
the  syringe  should  be  so  directed  that  the  stream 
will  go  past  the  object  and  behind  it  so  that  the 
stream  will  turn  back  against  the  object  and  carry 
it  back  out  of  the  ear.  If  an  insect  should  get  into 
the  ear,  it  must  be  killed  as  quickly  as  possible,  which 
can  be  done  by  a  few  drops  of  olive  or  sweet  oil  run 
into  the  ear.  The  oil  is  harmless  to  the  ear,  but  kills 
the  insect  by  getting  into  its  breathing  apparatus. 
The  insect  can  then  be  washed  out  with  warm  water 
as  described.  If  it  becomes  necessary  to  use  an  in- 
strument in  removing  the  insect,  it  would  be  safer 
to  go  to  a  physician  or  surgeon.  The  wax  of  the 
canal  usually  works  out  of  the  ear  about  as  fast  as  it 
is  formed.  When  this  is  the  case,  no  attempt  should 
be  made  to  clean  out  the  canal  with  either  water  or 
instruments.  It  is  sufficient  to  keep  clean  the  external 
ear  as  far  as  the  opening  of  the  canal.  Sometimes 
the  wax  does  not  come  out  as  it  should,  but  may 
accumulate  and  gather  into  a  hard  mass,  which  may 
affect  the  hearing  and  become  the  source  of  serious 


CARE    OF   THE  EAR  1 6? 

trouble.  In  such  cases  the  wax  should  be  removed  by 
a  physician. 

A  blow  on  the  side  of  the  head  may  affect  the  hear- 
ing. It  has  been  known  to  rupture  the  membrane  of 
the  drum  by  compressing  the  air  and  driving  it  inward. 

Inflammation  of  the  mucous  membrane  of  the  throat, 
as  in  colds  or  catarrh,  may  extend  along  the  Eustachian 
tube  to  the  middle  ear,  where,  if  long  continued,*  it  may 
produce  serious  trouble  which  can  not  be  cured.  Early 
attention  should  be  given  such  troubles.  The  parts  of 
the  ear  are  so  deep  in  the  head  that  they  are  very 
difficult  to  get  at,  consequently  only  those  skilled  in 
such  matters  ought  to  attempt  to  cure  any  trouble. 

It  is  best  not  to  try  without  the  advice  of  a  physician 
any  advertised  remedy  for  troubles  with  the  ear  or 
hearing,  and  especially  not  to  put  any  such  medicines  or 
other  objects  into  the  ear.  In  case  of  earache  or  pain 
in  the  region  of  the  ear,  the  simple  remedy  of  apply- 
ing a  hot-water  bag  or  heated  dry  cloths  may  be  used 
to  relieve  the  pain  until  the  proper  treatment  can  be 
given. 


CHAPTER    XIX 

DISEASE,    ITS    CAUSES   AND   PREVENTION 

THE  word  "  disease"  is  used  as  a  general  term  for  any 
form  of  wrong  action  of  one  or  more  parts  of  the  body. 
Only  a  single  part  may  be  diseased,  as  the  heart  or  eye, 
or  the  whole  body  may  be  affected.  Even  when  but 
a  single  part  is  diseased,  the  rest  of  the  body  may  feel 
some  of  the  effects. 

Perhaps  no  one  can  always  be  safe  from  every  form 
of  disease.  Yet  if  the  cause  of  a  disease  is  known, 
we  can  surely  be  better  defended  against  it.  In  study- 
ing the  various  organs  and  how  to  take  care  of  them, 
the  way  to  avoid  certain  diseases  of  these  organs  was 
shown.  At  this  place  we  will  point  out  some  general 
facts  to  help  us  avoid  other  forms  of  disease.  It  can 
not  be  said  too  strongly  or  too  often  that  impure  air, 
bad  food,  lack  of  exercise,  and  lack  of  sleep  are  among 
the  most  frequent  causes  of  diseases.  As  long  as  one 
of  these  causes  remains,  perfect  health  is  impossible. 
When  any  of  these  things  is  the  cause  of  disease,  no 
medicine  will  effect  a  cure.  The  thing  to  do  is  to 
remove  the  cause. 

The  Power  of  the  Body  against  Disease.  — The 
body  has  a  certain  amount  of  power  in  itself  to  con- 
tend against  disease.  The  more  vigorous  and  healthy 
the  body  is,  the  greater  its  power  to  keep  out  disease 

1 68 


INFECTIOUS  DISEASES  169 

or  to  cure  it  if  it  gets  a  start.  We  all  know  that  wounds, 
bruises,  and  sprains  get  well  from  what  the  body 
itself  does  to  cure  them.  All  that  can  be  done  outside 
the  body  is  to  help  a  little  by  keeping  the  parts  clean 
and  comfortable,  and  by  guiding  the  repair,  so  that,  for 
example,  a  joint  may  not  become  crooked  in  healing. 
So  with  more  serious  diseases  the  cure  depends  on 
the  powers  of  the  body  to  contend  with  the  disease 
and  right  itself  again.  We  can  only  help  the  body 
in  its  fight  with  the  disease;  we  can  not  supply  any 
new  power  for  healing  that  the  body  itself  does  not 
possess. 

It  is  plain,  then,  that  the  most  important  protection 
against  disease  is  to  keep  the  body  at  all  times  best 
prepared  to  fight  it.  This  is  done  by  keeping  it  in  the 
best  condition  of  health.  Good  health  prevents  many 
forms  of  disease,  and  gives  the  body  the  best  chance 
of  getting  through  safely  those  it  can  not  prevent. 

Infectious  Diseases.  —  In  recent  years  great  dis- 
coveries have  been  made  concerning  the  causes  of 
many  of  the  most  dreaded  diseases.  It  has  been 
found  out  that  they  are  caused  by  very  minute  living 
organisms,  some  being  plants  and  others  animals, 
which  get  into  the  body  and  live  and  grow  in  the 
blood  or  other  liquids  in  the  body.  The  word  "  infec- 
tion" means  getting  some  of  these  organisms  started 
to  grow  in  the  body.  The  diseases  caused  in  this  way 
are  called  infectious  diseases.  The  little  organisms, 
which  will  grow  in  the  blood  and  cause  disease,  are 
sometimes  called  disease  germs.  It  is  very  important 
to  know  something  about  the  way  these  minute  organ- 
isms live,  so  as  to  be  able  to  avoid  them  or  destroy  them. 


I/O      DISEASE,   ITS   CAUSES  AND  PREVENTION 

Bacteria.  —  There  are  many  kinds  of  disease  germs. 
One  group  of  them  belongs  to  the  most  minute  of  all 
kinds  of  plants  called  bacteria.  Most  kinds  of  bac- 
teria are  so  very  small  that  they  can  be  seen  only 
with  a  good  microscope.  Millions  of  them  might  exist 
in  a  small  drop  of  liquid.  Very  many  kinds  of  bac- 
teria are  harmless,  but  some  of  them  are  very  harmful, 
causing  the  death  every  year  of  great  numbers  of 
people.  A  knowledge  of  how  some  of  the  harmless 
bacteria  grow  outside  of  the  body  will  teach  us  how 
the  disease-making  bacteria  grow  inside  of  the  body, 
and  how  the  body  gets  injections  diseases. 

If  a  cup  of  soup,  or  of  any  kind  of  liquid  contain- 
ing juices  of  plants  or  animals,  be  set  aside  in  a  warm 
place,  in  a  day  or  more  it  "  spoils,"  as  we  say.  That 
is,  it  gets  a  bad  taste,  or  a  bad  smell,  and  is  no  longer 
fit  to  eat.  Now  if  a  drop  of  the  liquid  is  examined 
properly  with  a  good  microscope,  millions  of  minute 
bacteria  will  be  found  in  the  liquid.  These  little  plants 
in  growing  have  fed  upon  the  soup  and  changed  much 
of  it  to  the  bad-smelling  and  bad-tasting  substances. 
It  has  been  proved  that  there  are  so  many  of  these 
kinds  of  bacteria  mingled  with  dust  in  the  air  that  some 
are  sure  to  fall  into  everything  left  open  to  them. 
When  they  fall  into  liquids  which  contain  substances 
good  for  their  food,  they  grow,  and  use  up  that  food. 
Meat  juices  are  food  for  such  bacteria.  If  a  cup  of 
soup  boiled  so  as  to  kill  the  bacteria  be  placed  where 
it  is  impossible  for  bacteria  to  fall  into  it,  it  will  "  keep." 
That  is  the  way  we  "  can  "  foods.  They  are  heated  to 
kill  the  bacteria  and  sealed  up  so  that  no  more  can  get 
to  them  and  spoil  them.  If  we  take  some  soup  which 


BACTERIA  171 

has  no  bacteria  in  it,  and  which  is  kept  carefully  away 
from  bacteria  that  may  fall  into  it  from  the  air,  and 
put  in  it  a  drop  of  soup  having  bacteria,  it,  too,  will 
soon  be  rilled  with  bacteria  and  will  be  spoiled.  This 
would  happen  if  we  took  the  minutest  quantity  of  soup 
containing  bacteria  on  the  fine  point  of  a  needle  and 
touched  the  good  soup  with  it.  This  is  because  the 
bacteria  are  plants.  Putting  a  few  bacteria  in  a  cup 
of  good  soup  is  really  planting  them  there,  and  like 
all  plants  they  grow  and  produce  more  plants  like 
themselves.  This  they  do  very  rapidly.  If  the  seeds 
of  some  weed  are  planted  in  a  field,  that  weed  may 
become  so  abundant  that  it  will  cover  the  field  in  the 
course  of  a  few  years.  Bacteria  grow  so  rapidly  that 
they  can  fill  their  field  in  a  day  or  so. 

The  disease  bacteria  live  and  grow  in  the  same  way 
as  do  those  which  spoil  the  soup,  but  they  grow  in  the 
blood  of  man  by  using  it  or  other  juices  in  the  body 
as  food  and  leaving  in  it  poisonous  substances.  Thus 
they  cause  disease.  Now,  the  most  important  thing  to 
know  about  the  disease-making  bacteria  is  that  they 
can  not  appear  in  the  body  unless  they  are  planted 
there ;  that  is,  they  must  be  brought  from  some  place 
oustide  of  the  body.  If  then  we  keep  all  disease- 
making  bacteria  from  entering  the  body,  the  body  will 
always  be  free  from  the  bacteria  diseases.  In  this 
way  the  blood  of  the  body  is  like  the  cup  of  soup 
spoken  of  above.  But  if  ever  so  small  a  quantity  of 
substance  from  a  body  that  has  the  disease-making  bac- 
teria in  it,  comes  in  contact  with  the  blood  of  the 
healthy  body,  the  disease  bacteria  may  grow  and  in- 
crease in  it  until  the  body  becomes  diseased.  We  have 


1/2      DISEASE,   ITS   CAUSES  AND  PREVENTION 

spoken  only  of  bacteria  producing  disease,  but  there 
are  also  some  very  minute  animals  which  produce  dis- 
ease in  much  the  same  way  as  do  the  disease  bacteria. 
For  just  the  same  reasons  we  can  say  that  diseases 
made  by  them  will  not  occur  if  we  keep  these  little 
living  animals  away  from  the  body. 

Prevention  of  Infectious  Diseases.  —  Since  the  dis- 
covery that  some  of  the  most  severe  diseases  are  caused 
by  minute  plants  or  animals,  very  much  study  has  been 
given  to  finding  out  just  the  kind  of  disease  germ  that 
is  the  cause  of  each  kind  of  disease,  and  just  how 
that  particular  kind  gets  from  one  body  to  another. 
When  this  is  known  then  we  can  keep  diseases  from 
spreading.  If  every  one  knew  these  facts  and  all 
would  help,  we  could  stamp  out  completely  many  of 
these  diseases.  This  shows  us  how  important  it  is  to 
know  of  these  things.  There  is  much  yet  to  be  learned, 
but  much  has  already  been  found  out  which  has 
helped  very  greatly  to  save  lives.  In  civilized  coun- 
tries now  there  are  public  officers  whose  duty  it  is  to 
try  to  prevent  the  spread  of  diseases.  In  this  country 
they  are  the  boards  of  health  and  other  health  officers. 
When  any  one  gets  sick  with  an  infectious  disease,  the 
physicians  and  the  health  officers  plan  according  to 
the  particular  kind  of  disease  to  keep  the  germs  from 
getting  to  any  one  else.  Everybody  should  help  them 
in  every  way  and  keep  all  their  rules;  for  if  any  one 
breaks  their  rules  he  may  not  only  become  sick  him- 
self, but  he  may  be  the  means  of  much  sickness  and 
suffering  to  others  as  well. 

Examples  of  Infectious  Diseases.  —  It  is  not  a  proper 
place  in  this  book  to  describe  the  details  of  diseases 


DIPHTHERIA  1 73 

and  explain  methods  of  curing  them.  But  it  may 
make  matters  clearer  if  some  examples  of  these  diseases 
are  mentioned,  and  some  of  the  general  facts  about 
them  given. 

Diphtheria. — This  is  one  of  the  most  dreaded  dis- 
eases caused  by  bacteria.  The  linings  of  the  throat, 
nose,  and  air  passages  become  inflamed  and  false 
growths  take  place  in  them.  The  parts  affected  are 
crowded  with  the  bacteria  of  diphtheria.  Any  minute 
particles  from  these  parts  have  bacteria  of  diphtheria 
in  them,  which  will  start  the  same  growth  in  another 
person's  throat.  These  little  particles  in  coughing  may 
get  upon  the  things  in  the  room  about  the  patient. 
They  may  get  on  the  vessels  he  drinks  out  of  or  eats 
from.  By  these  means,  or  by  common  house  flies, 
they  may  be  carried  away  to  other  houses.  For  these 
reasons  it  can  be  understood  why  the  person  sick  with 
diphtheria  must  be  kept  away  from  all  except  those 
who  care  for  him.  All  the  clothing  and  things  used 
by  him,  or  by  his  nurses,  and  the  whole  room  must 
be  thoroughly  cleaned  and  all  the  bacteria  on  them 
killed.  If  it  is  known  soon  enough  that  one  has  this 
disease,  and  all  this  care  is  taken,  until  the  proper  time 
after  the  patient  is  well,  no  other  case  will  start  from 
this  one;  but  if  proper  care  is  neglected  in  this  case, 
the  disease  may  spread  rapidly  and  many  deaths  may 
occur  from  it.  In  such  cases  every  one  should  always 
remember  how  much  harm  may  come  from  his  care- 
lessness. 

Scarlet  Fever,  Measles,  Erysipelas,  and  Smallpox  are 
also  examples  of  diseases  that  are  spread  by  particles 
from  the  body  of  the  sick  person  which  contain  the 


1/4      DISEASE,   ITS   CAUSES  AND  PREVENTION 

germs  of  the  disease.  These  are  carried  by  touch, 
clothing,  or  other  things  used  by  the  sick  one.  The 
same  rules  should  be  followed  with  these  diseases  as 
with  diphtheria. 

Vaccination.  — Many  years  ago  Dr.  Jenner  made  a 
great  discovery  in  regard  to  smallpox.  It  was  known 
that  a  person  who  had  once  had  smallpox  did  not 
easily  take  it  the  second  time,  for  some  years  at  least. 
He  found  a  way  of  giving  a  very  slight  attack  of  small- 
pox by  vaccination.  This  made  the  person  not  liable 
to  take  smallpox  for  several  years,  and  if  he  did  take 
it  he  had  it  very  lightly.  The  practice  of  vaccination 
is  universal  in  civilized  countries.  It  has  saved  great 
numbers  of  lives  and  an  immense  amount  of  suffering. 
Before  this  discovery  great  epidemics  of  smallpox 
frequently  occurred.  Now  in  countries  where  vac- 
cination is  used  only  a  few  cases  occasionally  are  known. 
Vaccination  not  only  helps  the  person  vaccinated  by 
keeping  him  from  taking  smallpox,  but  helps  the  whole 
community,  for  if  there  are  some  in  the  community 
not  vaccinated  there  is  always  a  chance  for  smallpox 
to  get  a  start  there.  Much  study  is  being  made  to 
find  means  of  doing  for  other  diseases  what  vaccina- 
tion does  for  smallpox. 

Consumption,  Tuberculosis  of  the  Lungs.  —  This 
disease  is  caused  by  a  certain  kind  of  bacteria  which 
gets  into  the  lungs  by  breathing.  The  disease  is  spread 
by  bacteria  from  the  lungs  of  the  sick  person.  They 
pass  from  the  lungs  to  the  miicus  which  is  coughed 
up  and  spit  out.  Particles  of  dried  sputa  may  get 
into  the  air  with  the  dust  and  thus  may  be  breathed 
into  the  lungs.  If  all  the  substance  thrown  off  from 


TYPHOID  FEVER  1/5 

the  throat  and  lungs  of  the  patient  were  caught  in 
cloths  or  vessels  and  destroyed,  there  would  be  little 
danger  of  communication  of  the  disease.  If  the  direc- 
tions of  physicians  in  regard  to  this  disease  were 
carried  out  carefully,  it  would  soon  cease  to  be  so 
widespread  as  it  is  now.  This  disease  is  an  example 
of  one  that  can  usually  be  prevented  by  keeping  the 
general  health  good  and  especially  by  taking  good  care 
to  have  plenty  of  pure  air.  Outdoor  life  is  considered 
the  best  medicine  for  consumptives.  Therefore  out- 
door life  must  be  a  good  preventive  of  the  disease. 

Typhoid  Fever.  — This  disease  is  caused  by  a  kind 
of  bacteria.  They  grow  in  the  intestines.  A  person 
takes  typhoid  fever  by  swallowing  some  of  the  typhoid 
fever  bacteria  with  his  food  or  drink.  How  the  bac- 
teria get  in  the  food  or  drink  has  sometimes  been  a 
great  puzzle.  But  in  many  cases  where  people  in  a 
town  have  been  taken  sick  with  typhoid  fever  the 
puzzle  has  been  solved.  In  some  cases  it  was  found 
that  they  had  all  drunk  water  that  had  typhoid  bac- 
teria in  it,  and  that  these  bacteria  had  come  from 
letting  discharges  from  the  bowels  of  typhoid  fever 
patients  get  into  the  source  of  the  water  supply.  In 
other  cases  the  fever  came  from  drinking  milk  from 
an  unclean  dairy.  The  dairy  people  had  washed  their 
cans  with  water  that  was  contaminated  with  the  dis- 
charge of  typhoid  fever  patients.  In  other  cases  the 
bacteria  have  been  carried  from  the  discharges  of  sick 
people  to  the  food  of  other  people  by  the  common 
house  fly.  By  such  examples  and  others  it  has  been 
proved  that  typhoid  fever  bacteria  in  some  such  ways 
always  came  from  typhoid  fever  patients.  This  shows 


1/6     DISEASE,   ITS   CAUSES  AND  PREVENTION 

the  danger  in  sewers,  and  the  importance  of  destroying 
all  discharges  of  typhoid  fever  patients.  During  an 
epidemic  of  typhoid  fever  one  may  be  safe  if  he  is 
careful  to  eat  no  food  that  has  not  been  cooked  at 
home  and  drink  no  water  or  milk  that  has  not  been 
boiled.  Heat  kills  the  bacteria. 

Cholera.  — This  disease  also  is  caused  by  a  kind  of 
bacteria  growing  in  the  intestines.  The  cholera  bac- 
teria, like  the  typhoid  fever  bacteria,  can  be  carried  by 
food,  by  flies,  by  drinking  water,  or  by  milk.  The, 
most  usual  means  is  by  the  water  used  for  drinking. 

Water  Supply  for  Drinking.  —  There  are  other  kinds 
of  germs  that  can  be  carried  by  water,  which  cause 
intestinal  troubles.  Since  this  is  the  case,  the  water 
supply  for  drinking  should  be  most  carefully  guarded. 
If  it  is  from  springs  or  wells  it  should  be  seen  to  that 
there  is  no  possible  chance  for  the  drainage  of  any 
filthy  places  getting  to  them.  Sometimes  the  soil  is 
such  that  it  will  allow  water  from  these  sources  to  soak 
through  it  a  long  distance.  In  this  way  the  well  may 
become  polluted  when  there  does  not  seem  to  be  any- 
thing wrong  with  it.  When  cities  get  their  water  from 
lakes  or  streams,  disease  germs  may  get  to  the  supply. 
We  have  to  depend  on  the  health  officers  to  take  care 
of  us  in  such  cases  by  the  means  that  they  have  for 
the  remedy.  If  at  any  time  there  may  be  danger  from 
the  water,  it  should  be  boiled  before  being  used  for 
drinking  or  for  washing  dishes  or  anything  which  may 
get  to  our  mouths. 

Malaria.  — Malaria  is  also  known  as  "  fever  and 
ague,"  "  chills  and  fever,"  and  it  has  other  names  as 
well.  There  are  different  forms  of  malaria.  Within 


YELLOW  FEVER  1/7 

the  past  few  years  it  has  been  found  that  certain  kinds 
of  mosquitoes  are  the  means  of  carrying  malaria  about. 
The  minute  germs  of  malaria  live  part  of  their  life  in 
this  mosquito  and  part  of  their  life  in  the  blood  of  man. 
When  a  man  is  sick  with  malaria,  the  little  organisms 
are  abundant  in  his  blood.  If  now  a  mosquito  of  this 
kind  bites  him,  it  draws  through  its  bill  with  the 
blood  of  the  man  many  of  the  malaria  organisms. 
Later  if  this  mosquito  bites  another  man,  the  disease 
germs  may  be  injected  into  his  blood  and  he  may  get 
malaria.  It  is  plain  then  that  if  we  could  in  any  re- 
gion destroy  all  of  the  malaria-carrying  mosquitoes, 
malaria  would  die  out.  We  can  see,  too,  how  a  man 
with  malaria  can  supply  mosquitoes  with  germs  to 
carry  to  other  people. 

Yellow  Fever.  —  This  disease  is  such  a  fearful  one 
that  its  appearance  frightens  all  in  the  community. 
It  has  been  recently  discovered  that,  like  malaria,  it 
is  caused  by  germs  carried  by  a  certain  kind  of  mos- 
quito. If  these  mosquitoes  are  kept  away  or  killed, 
there  is  no  danger  of  yellow  fever,  even  if  one  is  in  the 
same  room  with  the  patient.  The  well  person  should 
be  protected  from  the  mosquitoes,  so  that  he  can  not 
be  bitten  and  get  the  disease.  The  patient  must  be 
guarded  from  mosquitoes,  so  that  the  germs  can  not 
be  carried  from  him  to  others. 

The  way  one  person  may  start  a  yellow  fever  epi- 
demic in  a  large  region  is  as  follows :  If  there  has  been 
no  yellow  fever  in  a  region  for  some  time,  none  of  the 
mosquitoes  have  the  germs  of  the  disease  in  them. 
Now  some  one  from  a  yellow  fever  region,  who  has 
been  bitten  by  mosquitoes  with  yellow  fever  germs, 

IND.  PR.  PHYS.  —  12 


1/8     DISEASE,  ITS   CAUSES  AND  PREVENTION 

may  come  to  visit  this  region  before  the  disease  de- 
velops in  him.  Soon  he  is  taken  sick.  Through  neg- 
lect of  care,  or  ignorance  of  the  danger,  some  yellow 
fever  mosquitoes  may  get  to  him  and  bite  him.  Then 
they  bite  others  and  inject  the  yellow  fever  germs  into 
them,  other  mosquitoes  bite  the  new  patients,  and  so 
the  cases  of  yellow  fever  increase  with  alarming  rapidity. 
Fighting  Mosquitoes.  —  Not  all  kinds  of  mosquitoes 
carry  malaria  or  yellow  fever,  so  we  need  not  feel  afraid 
every  time  we  see  a  mosquito.  But  if  malaria  or  yellow 
fever  is  in  a  community,  it  is  time  to  look  after  the  mos- 
quitoes. Screens  and  netting  can  keep  them  out  of  the 
houses  by  using  much  care.  To  make  a  good  fight 
against  them  people  now  try  to  do  away  with  their 
breeding  places  or  kill  them  in  these  places.  As 
they  breed  in  water,  ditches,  ponds,  water  barrels,  old 
tin  cans  with  water  in  them,  all  furnish  good  places 
for  them  to  breed  in.  Mosquitoes  lay  eggs  in  these 
places,  the  eggs  hatch  into  "  wrigglers  "  or  "  wiggle- 
tails,"  as  they  are  called.  These  are  the  larva.  From 
the  "  wiggle-tails  "  the  mosquitoes  come.  If  the  breed- 
ing places  are  cleaned  up  or  drained  so  that  they  become 
dry,  of  course  no  mosquitoes  can  breed  in  them.  If 
the  places  can  not  be  drained  it  has  been  found  that 
the  larvae,  or  "  wiggle- tails,"  can  be  quickly  killed  by 
pouring  kerosene  on  the  water.  A  very  little  of  the 
oil  will  spread  out  in  a  very  thin  layer  over  a  large 
surface  of  water.  Now  the  larvae  must  come  to  the 
surface  to  breathe.  When  they  do  so  the  oil  kills 
them  instantly.  Thus  it  seems  as  if  we  have  a  way 
to  get  rid  of  these  very  dangerous  mosquitoes.  Frosts 
and  cold  weather  in  winter  help  us  part  of  the  year. 


WOUNDS  179 

New  cases  of  yellow  fever  or  malaria  do  not  appear 
after  a  few  heavy  frosts. 

Fighting  House  Flies.  —  Since  typhoid  fever  and 
cholera  may  be  brought  into  a  house  by  flies,  these 
should  be  shut  out  of  the  house  by  screens,  but  it  is 
also  easy  to  destroy  most  of  them  before' they  are  fully 
developed.  The  eggs  of  the  most  common  species  of 
house  flies  are  laid  in  the  refuse  of  the  horse  stable. 
This  refuse  should  be  frequently  removed  and  piled  in 
a  mass.  By  this  means  the  eggs  are  buried  and  the 
pupae  are  destroyed. 

Wounds.  —  When  studying  the  skin,  it  was  shown 
that  one  use  of  the  epidermis  is  to  keep  out  bacteria. 
There  seem  to  be  several  kinds  of  bacteria  which  will 
cause  inflammation  of  a  wound  'and  blood  poisoning. 
These  bacteria  may  be  present  in  various  kinds  of 
dirt  and  filth.  They  may  be  in  decaying  substances. 
When  they  get  on  our  skin  the  epidermis  keeps  them 
out  until  they  are  washed  off.  If,  however,  there  is 
a  break  in  the  epidermis  they  get  in  and  cause  trouble. 
It  is  best,  as  has  been  shown,  to  bathe  the  skin  fre- 
quently. The  hands  should,  of  course,  be  cleaned  im- 
mediately after  anything  with  dangerous  dirt  of  any 
kind  on  it  has  been  handled.  Cleanliness  makes 
the  body  at  all  times  safer  in  case  of  an  accidental 
wound.  But  even  if  the  body  is  clean,  the  object 
making  the  wound  may  have  some  of  the  dangerous 
kinds  of  bacteria  on  it  and  a  very  slight  wound  may 
in  this  way  become  very  serious.  Every  wound  should 
as  soon  as  possible  be  carefully  cleaned  and  kept  so. 
The  wound  should  be  washed  also  with  some  liquid 
that  has  been  prepared  for  such  a  purpose,  called  an 


180     DISEASE,   ITS   CAUSES  AND  PREVENTION 

antiseptic.  An  antiseptic  is  something  that  kills  bac- 
teria. Various  substances  are  used  as  antiseptics. 
Most  of  them  are  poisons,  and  should  be  used  only 
when  they  are  prepared  by  some  one  who  understands 
about  them,  with  careful  following  of  the  directions 
given.  When  the  wound  is  cleaned  of  bacteria,  the 
next  thing  is  to  keep  any  more  bacteria  from  getting 
into  it.  This  is  done  by  covering  it  with  cotton 
that  has  been  made  very  clean  for  this  purpose.  It 
is  called  absorbent  cotton.  If  the  wound  is  kept  care- 
fully covered  with  this,  all  bacteria  that  would  fall  on 
the  wound  are  caught  by  it.  If  one  receives  a  severe 
wound,  of  course  the  physician  should  be  asked  to  treat 
it.  Still  it  is  well  to  know  about  these  matters  so  that 
we  can  give  immediate  aid  to  the  injured,  and  can  follow 
the  physician's  directions  with  intelligence. 

When  a  surgeon  is  compelled  to  make  a  wound  in 
performing  an  operation,  he  is  careful  that  the  instru- 
ments he  uses,  his  clothing,  and  his  hands  are  as  free 
as  possible  from  bacteria.  The  room  is  also  made  clean. 
When  all  this  is  done  properly  and  the  wound  guarded 
against  bacteria  afterward,  it  will  heal  without  trouble. 
If  this  is  not  done,  the  most  severe  troubles  may  arise 
from  even  a  slight  wound. 


CHAPTER  XX 

ALCOHOL,  TEA,  COFFEE,  TOBACCO,  OPIUM 

IN  certain  chapters  throughout  this  book  we  have 
called  attention  to  the  effects  of  alcohol  on  the  spe- 
cial organs  there  described.  It  seems  desirable  now 
to  speak  of  the  effects,  on  the  body  as  a  whole,  of 
alcohol,  as  well  as  of  tea,  coffee,  tobacco,  and  opium. 
It  is  on  the  body  as  a  whole  that  the  most  injurious 
work  of  these  agents  is  to  be  seen.  These  substances 
are  so  widely  used,  and  the  consequences  of  their 
excessive  use  are  so  serious,  that  a  special  chapter 
may  well  be  devoted  to  a  discussion  of  their  effects 
in  the  hope  that  many  may  be  deterred  from  the  for- 
mation of  dangerous  habits  in  their  use. 

Description  of  Alcohol.  —  Alcohol  in  a  pure  state 
is  a  transparent  liquid.  It  is  somewhat  lighter  than 
water.  It  is  so  nearly  a  true  liquid  that  it  forms  no 
lasting  bubbles  when  shaken  up  in  a  bottle.  It  burns 
with  a  pale  blue  flame,  without  smoke,  thus  produc- 
ing a  great  amount  of  heat.  Pure  alcohol  is  known 
as  "  absolute  alcohol."  Alcohol  mixes  readily  with 
water  in  all  proportions.  The  alcohol  usually  sold, 
known  as  "  commercial  alcohol,"  generally  contains 
five  per  cent  or  more  of  water. 

Source  of  Alcohol.  —  Alcohol  is  formed  by  the 
growth  of  the  yeast  plant  in  solutions  containing 

181 


1 82     ALCOHOL,    TEA,    COFFEE,    TOBACCO,    OPIUM 

sugar.  When  yeast  is  placed  in  a  solution  contain- 
ing sugar  of  the  right  proportions,  and  it  is  kept  in 
a  warm  place,  the  yeast  grows  rapidly,  and  in  its 
growth  converts  the  sugar  into  alcohol  and  carbonic 
acid.  The  carbonic  acid,  being  a  gas,  generally 
bubbles  up  through  the  solution  and  escapes;  but  the 
alcohol  being  a  liquid  remains  dissolved  in  the 
solution." 

In  making  bread,  however,  the  carbonic  acid  re- 
sulting from  the  growing  yeast  is  held  by  the  sticky 
dough,  which  it  lifts  up  and  makes  "  light."  In  the 
process  of  baking,  both  the  carbonic  acid  and  the 
alcohol  are  driven  off. 

The  juices  of  ripe  fruits  contain  sugar.  If  these 
juices  are  left  exposed  so  that  the  minute  yeast  plants 
in  the  air  can  get  into  them,  they  undergo  a  process 
called  "  fermentation."  This  process  of  fermenta- 
tion is  the  growth  of  the  yeast  plants,  and,  as  just 
explained,  it  produces  carbonic  acid,  which  mainly 
escapes  from  the  juice  and  leaves  the  alcohol  remain- 
ing in  the  liquid.  Thus  the  juice  of  grapes  is  changed 
into  wine,  the  juice  of  apples  into  cider.  If  the  juices, 
after  the  formation  of  alcohol  in  them,  are  allowed 
to  stand  exposed  to  the  air,  other  minute  organisms 
grow  in  them,  which  will  change  the  alcohol  to  acetic 
acid.  Wine  and  cider  are  thus  changed  to  vinegar. 
Many  other  solutions  of  sugar  are  used  to  allow  the 
formation  of  alcohol,  and  thus  many  forms  of  alco- 
holic drinks  are  produced. 

Beer,  ale,  and  porter  belong  to  the  group  of  malt 
liquors.  In  making  these,  barley  is  kept  moist  and 
warm  till  it  begins  to  sprout.  In  the  act  of  sprout- 


PHYSIOLOGICAL   ACTION   OF  ALCOHOL          183 

ing,  the  starch  of  the  grain  is  changed  to  sugar.  The 
sprouted  grain  is  dried  and  ground  up,  and  water 
is  added,  which  dissolves  the  sugar  and  other  sub- 
stances of  the  grain.  To  this  solution  yeast  is  then 
added,  which  converts  the  sugar  into  alcohol  and 
carbonic  acid.  The  resulting  clear  liquid  containing 
the  alcohol  separated  from  the  undissolved  parts 
constitutes  beer,  ale,  or  porter,  the  distinctions  being 
due  to  certain  differences  of  treatment  in  the  manu- 
facture of  the  liquids. 

Another  class  of  alcoholic  drinks  is  produced  by 
first  allowing  alcoholic  fermentation  by  yeast  to  take 
place,  and  then  separating  the  liquor  by  distillation 
from  the  other  matters  in  the  mixture.  Examples 
of  such  drinks  are  whisky,  brandy,  rum,  and  gin. 
These  contain  a  far  greater  amount  of  alcohol  than 
the  wines  or  beer. 

The  quantity  of  alcohol  in  the  different  drinks 
varies  greatly.  In  some  kinds  of  beer  the  amount 
is  as  low  as  two  per  cent,  while  in  some  forms  of 
brandy  it  reaches  'fifty-five  per  cent.  In  all  alcoholic 
drinks,  however  much  they  differ  in  flavor,  the  alco- 
hol is  of  the  same  nature,  and  has  the  same  origin. 
The  different  flavors  by  which  the  various  alcoholic 
drinks  are  distinguished  are  due  mainly  to  substances 
extracted  from  the  materials  used  in  their  manu- 
facture. The  most  characteristic  effects  resulting 
from  the  use  of  alcoholic  drinks  are  due  to  the  alco- 
hol contained  in  them. 

Physiological  Action  of  Alcohol.  —  In  considering 
the  physiological  effects  of  alcohol,  there  are  certain 
facts  which  must  be  kept  in  mind. 


1 84    ALCOHOL,    TEA,    COFFEE,    TOBACCO,    OPIUM 

First,  there  is  the  great  difficulty  of  determining 
the  exact  effect,  on  any  special  organ,  of  any  sub- 
stance taken  as  food,  medicine,  or  poison.  We  can 
usually  say  that  a  certain  food  is  good  or  bad  be- 
cause, when  it  is  used  constantly,  the  general  health- 
of  the  body  is  improved  or  impaired.  But  it  would, 
in  most  cases,  be  impossible  to  tell  the  special  effect 
of  that  food  on  the  various  tissues.  Of  course,  in  all 
such  cases,  there  are  people  ready  to  advance  theo- 
ries to  explain  the  exact  action  of  the  various  foods 
on  each  of  the  tissues.  But  explanations  which 
have  not  been  experimentally  proved  are  of  no  value. 
There  are  many  medicines  whose  general  tendencies 
are  pretty  clearly  known,  but  whose  special  effects  on 
the  cells  of  any  tissue  are  wholly  unknown.  Quinine 
is  a  good  example.  It  is  well  known  that  if  given  in 
a  proper  way  it  will,  in  a  grqat  number  of  cases,  cure 
certain  diseases;  but  it  is  impossible  to  say  definitely 
how  the  cure  is  effected,  and  it  certainly  is  not  pos- 
sible to  show  with  microscopic  sections  any  changes 
in  the  tissues  produced  by  such  small  quantities  of 
quinine. 

Some  of  the  most  active  poisons,  while  they  show, 
by  causing  death,  their  sure  and  speedy  effect  on  the 
body  as  a  whole,  give  no  indication,  under  the  most 
careful  examination,  of  their  special  action  on  the 
various  tissues  of  the  body. 

There  is  no  doubt  that  when  any  substance,  as  a 
food,  a  medicine,  or  a  poison,  produces  an  effect  on 
the  body,  it  does  so  by  causing  certain  changes  in  the 
cells  of  some  or  all  of  the  tissues.  But  what  these 
changes  are,  it  is  usually  impossible  to  determine. 


PHYSIOLOGICAL  ACTION  OF  ALCOHOL          185 

A  second  fact  that  should  be  kept  in  mind  in  con- 
sidering this  subject  is  that  individuals  vary  greatly 
in  the  way  they  are  affected  by  different  kinds  of 
foods  and  drugs.  Often  it  is  found  that  a  food  that 
seems  beneficial  or  harmless  to  most  people  may  pro- 
duce in  certain  individuals  unpleasant  or  distressing 
symptoms.  A  drug  that  may  powerfully  affect  a  ma- 
jority of  people  may  be  used  by  a  few  without  marked 
injurious  results.  Even  the  effects  that  generally  follow 
the  use  of  any  drug  vary  greatly  in  character  and  de- 
gree in  different  persons.  Hence  we  must  not  draw 
any  definite  conclusions  from  a  single  experience  or 
from  a  few  observations  on  a  few  individuals. 

A  third  fact  important  to  remember  is  this:  The 
effects  of  substances  may  vary  under  different  condi- 
tions ;  as,  in  various  degrees  of  health,  in  connection 
with  different  kinds  of  diet,  in  activity  or  rest  of  the 
body,  in  different  climates,  and  in  different  ages. 
In  view  of  these  facts,  the  following  statements  of 
the  physiological  effects  of  alcohol  must  of  necessity 
be  of  a  general  character,  and  they  can  not  be  made 
applicable  to  each  individual  case. 

If  a  small  amount  of  alcohol  is  taken,  it  may  pro- 
duce no  perceptible  effect  except  a  slight  increase  of 
the  pulse  rate.  -^ 

The  effects  of  large  amounts  of  alcohol  are  well 
summed  up  by  Dr.  Emerson,  as  follows: 

"  If  large  doses  be  given  a  healthy  person,  the 
usual  course  is,  first,  a  flushing  of  the  face,  with  a 
greater  flow  of  words  and  ideas,  and  tendency  of 
muscular  activity;  then  imperfect  articulation,  loss 
of  judgment,  unsteady  gait,  dulled  moral  sense,  irregu- 


1 86  ALCOHOL,  TEA,  COFFEE,  TOBACCO,  OPIUM 

lar  eyesight,  loss  of  sensation,  then  of  consciousness, 
and,  finally,  even  impaired  (vegetative  functions) 
breathing  and  circulation  —  all  of  these  phenomena 
being  successive  paralyses  of  nervous  centers  of  the 
brain,  medulla,  and  spinal  cord. 

"  If  large  doses  be  often  repeated,  the  alcohol  car- 
ried through  the  various  organs  modifies  their  nutri- 
tion and  the  growth  of  the  mere  connecting  tissues 
(framework)  at  the  expense  of  their  more  important 
special  tissues.  Thus  the  stomach  and  liver,  kidneys, 
and,  finally,  even  the  voluntary  muscles,  and  the 
all-important  involuntary  muscle  called  the  heart, 
degenerate.  These  processes  are  slow  and  only  result 
from  the  decided  abuse  of  alcohol,  especially  spirits." 

The  student  is  referred  to  the  chapters  on  circula- 
tion (p.  52),  foods  (p.  70),  and  the  nervous  system 
(p.  130),  for  a  description  of  the  special  effects  on 
these  organs  of  the  use  of  alcohol.  But  to  under- 
stand the  full  action  of  alcohol  on  the  body  as  a  whole, 
we  must  remember  that  the  results  described  for  these 
various  organs  occur  all  together.  These  organs,  as 
we  have  learned,  have  very  important  functions. 
When  the  action  of  one  is  interfered  with,  its  effect 
is  felt  on  the  whole  body,  and  thus  the  direct  injury 
occasioned  by  alcohoHs  heightened.  If  the  functions 
of  these  important  organs  are  being  interfered  with, 
the  general  health  of  the  body  is  sure  to  be  under- 
mined. The  capability  of  the  body  for  accomplish- 
ing physical  or  'mental  work  is  greatly  lessened.  Its 
power  of  resisting  the  attacks  of  disease  is  decreased. 
Its  power  of  recovery  when  disease  has  invaded  the 
system  becomes  much  weakened.  This  condition  of 


ALCOHOL   AS  A   MEDICINE  1 87 

the  body  is  sometimes  described  as  "  an  undermined 
constitution "  or  "  a  lowered  vitality."  While  it  is 
hard  to  describe  accurately  what  has  occurred  to  the 
body,  the  condition  is  none  the  less  real.  It  can  be 
easily  recognized,  and  is  indeed  a  serious  matter. 

If  the  body  sustains  accidental  injury,  or  if  for  some 
cause  a  surgical  operation  is  to  be  performed,  the 
surgeon  realizes  that  recovery  is  likely  to  be  less  speedy, 
or  less  sure,  if  the  patient  has  been  accustomed  to  the 
use  of  alcoholic  drinks. 

Under  training  for  any  athletic  contest,  experi- 
ence has  shown  that  the  greatest  success  can  not  be 
secured  when  alcoholic  drinks  are  indulged  in;  con- 
sequently their  use  is  forbidden.  In  cases  where 
long-continued,  severe  bodily  exertion  is  necessary, 
or  an  unusual  amount  of  exposure  to  fatigue,  cold, 
or  heat,  experience  has  also  shown  that  the  drinking 
of  alcohol  is  detrimental.  In  these  cases  the  objec- 
tion to  the  use  of  alcohol  is  clear.  Still  the  effects 
are  the  same  whether  we  are  engaged  in  a  severe 
contest  or  not.  We  are  all  the  time  in  some  sort 
of  contest,  and  certainly  each  one  wishes  to  be  at 
his  best.  Experience  shows  clearly  that  we  are  not 
at  our  best  after  using  alcohol.  The  same  may  be 
said  of  the  use  of  tea,  coffee,  and  opium,  and  its  com- 
pounds. 

Alcohol  as  a  Medicine.  — The  discussion  of  the 
question  as  to  whether  alcohol  may  be  beneficial 
in  the  treatment  of  disease  is  out  of  place  here. 
When  we  are  sick  we  should  be  put  under  the  care 
of  a  well-trained  physician.  Then  we  must  trust  to 
his  learning  and  skill,  and  follow  his  directions.  The 


1 88     ALCOHOL,    TEA,    COFFEE,    TOBACCO,    OPIUM 

forms,  conditions,  degrees,  and  courses  of  diseases  are 
so  varied,  and  so  obscure,  that  it  would  generally  be 
dangerous  to  trust  ourselves  to  any  one  not  trained 
or  skilled  in  the  practice  of  medicine.  There  are 
many  poisons  and  other  injurious  substances  that 
may  be  used  with  great  benefit  in  certain  conditions 
or  phases  of  disease.  Physicians  differ  in  opinion  as 
to  whether  alcohol  is  one  of  them.  But,  in  any  case, 
the  problem  must  be  solved  by  the  physicians,  and, 
however  settled,  it  will  not  affect  the  question  of  the 
effect  of  alcohol  on  the  healthy  body. 

Other  Substances  in  Alcoholic  Drinks.  —  Thus  far 
we  have  spoken  only  of  the  alcohol  in  alcoholic  drinks, 
but  they  contain  a  number  of  other  substances.  Some 
of  these  occur  naturally,  and  others  are  added  either  to 
change  the  flavor  or  as  adulterations.  Some  of  these 
are  known  to  be  injurious  and  others  to  be  harmless. 
The  number  of  these  substances  is  so  great  that  a  special 
treatment  of  each  is  impossible  here. 

Intoxication.  — Thus  far  we  have  dwelt  mainly  on 
the  effects  of  long-continued  use  of  alcohol  on  the 
general  health  of  the '  body.  There  is,  however,  one 
result  which  is  so  evident  that  neither  physiologist 
nor  physician  is  needed  to  detect  it  or  to  point  out 
its  evils;  that  is,  the  intoxicating  effect  of  alcohol 
taken  in  large  doses.  This  is  known  in  common  lan- 
guage as  getting  drunk.  The  evils  of  drunkenness 
are  so  great  and  so  well  known  that  we  need  not  dwell 
on  them  here.  Fortunately,  a  large  number  of  those 
who  use  alcoholic  drinks  do  not  become  habitual 
drunkards.  However,  it  is  of  the  greatest  importance 
that  the  fact  be  emphasized  that  the  moderate  use 


EFFECTS   OF  ALCOHOLIC  DRINKING  189 

is  in  danger  of  becoming  immoderate.  It  is  only  from 
the  ranks  of  the  moderate  users  that  the  great  army  of 
drunkards  is  recruited.  It  is  impossible  for  a  man  to 
foretell,  when  forming  the  habit  of  drinking,  whether 
or  not  he  will  be  able  to  control  himself  from  running 
into  excess.-  Hence  when  ajnan  cultivates  this  habit 
he  runs  this  risk. 

It  would  seem  as  if  no  person  who  has  contem- 
plated the  terrible  things  which  have  been  done  under 
intoxication  would  voluntarily  assume  a  habit  which 
involved  even  the  bare  possibility  of  such  an  end. 
Indeed,  all  such  arguments  against  the  use  of  alcohol 
as  those  contained  in  the  facts  of  its  effect  on  the 
heart,  the  kidneys,  or  the  liver,  or  on  the  general 
health,  pale  before  .the  undisputed  evidence  that 
by  means  of  alcohol  an  intelligent  man  may  act  with- 
out reason;  that  a  kind-hearted  man  may  become 
brutal  to  his  most  loved  friends;  that  an  honorable 
man  may  become  dishonorable;  that  a  man  with  a 
noble  nature  may  acquire  the  most  depraved  tastes; 
that  its  use  has  over  and  over  again  been  the  cause 
of  bitter  disappointments,  of  intense  sufferings,  and 
of  crime. 

Effects  of  Alcoholic  Drinking  on  the  Community.  - 
It  has  been  shown  beyond  doubt,  by  repeated  study 
of  statistics  gathered  from  prisons,  insane  asylums, 
and  almshouses,  that  the  use  of  alcoholic  drinks 
is  the  most  frequent  cause  of  crime,  insanity,  and 
poverty.  These  facts  are  so  well  known,  and  have 
been  before  us  so  long,  that  they  do  not  impress  the 
general  community  in  proportion  to  their  enormity. 
If  some  new  form  of  drug  or  food,  or  some  new  politi- 


IQO     ALCOHOL,    TEA,    COFFEE,    TOBACCO,    OPIUM 

cal  or  social  movement,  were  introduced  which,  in  a 
year  after  its  introduction,  would  bring  about  in  the 
civilized  world  physical  and  moral  results  as  harmful 
as  those  produced  by  alcohol,  the  fact  would  stir  every 
class  up  to  arms.  There  would  be  a  universal,  ener- 
getic, and  immediate  movement  toward  its  suppres- 
sion. 

Most  other  poisons  so  affect  their  victims  that  they 
alone  suffer  the  consequences  of  their  use.  But 
alcohol  renders  its  slaves  active  agents  in  bringing  suf- 
fering and  degradation  on  others  in  the  community. 
Other  vices  are  the  usual  associates  of  drunkenness. 

The  evil  influences  of  most  drinking  places  and  of 
many  drinking  customs  are  well  known  and  undis- 
puted. Thus  alcohol  comes  to  affect  not  individuals 
alone,  but  the  moral  tone  of  the  community  as  a  whole. 
In  these  facts,  again,  we  are  forcibly  shown  that  argu- 
ments against  the  use  of  alcohol  based  on  moral  grounds 
far  outweigh  all  those  drawn  from  physiological  con- 
siderations. 

Tea  and  Coffee.  —  Tea  consists  of  the  dried  leaves 
of  a  plant  extensively  cultivated  in  China,  Japan, 
Ceylon,  and  India.  The  leaves  contain  a  number 
of  vegetable  substances  common  to  all  leaves,  but  in 
addition  they  contain  an  alkaloid  known  as  theine, 
which  is  characteristic  of  tea  leaves.  There  is  also  a 
large  amount  of  tannin. 

Coffee  consists  of  the  seeds  or  so-called  "  berries  " 
of  a  plant  which  is  cultivated  for  drinking  purposes. 
The  berries  are  roasted,  and  by  this  means  an  aro- 
matic substance  is  developed  which  gives  coffee  its 
peculiar  flavor.  Besides  this  aromatic  substance  there 


TEA   AND    COFFEE  IQI 

are,  of  course,  many  other  ingredients  in  the  berries, 
prominent  among  which  are  tannin,  certain  vegetable 
acids,  and  caffeine. 

Theine  and  Caffeine.  —  It  is  to  these  substances 
that  the  characteristic  physiological  effects  of  tea 
and  coffee  are  due.  Theine  and  caffeine  are  exactly 
alike  in  their  chemical  composition,  and  the  same 
physiological  effects  have  been  assigned  to  both.  In 
tea  there  is  a  greater  amount  of  tannin.  This  has  an 
injurious  action  on  the  digestive  processes. 

After  speaking  of  the  beneficial  effects  of  a  mod- 
erate use  of  tea  for  some  persons,  Dr.  Yeo  says: 

"  On  the  other  hand,  it  is  quite  certain  that  tea 
taken  in  excess,  and  in  some  constitutions,  may  be- 
come very  injurious.  It  will  not  infrequently  excite 
and  maintain  most  troublesome  gastric  catarrh,  the 
only  remedy  for  which  is  an  entire  abstinence  from 
tea  for  a  considerable  period.  It  is  often  also  the 
cause  of  troublesome  cardiac  palpitations,  together 
with  muscular  tremors  and  general  nervous  agita- 
tion. We  have  noticed  that  tea  will  often  commence 
somewhat  suddenly  to  disagree  with  a  person,  and 
excite  dyspeptic  symptoms,  coincidently  with  the 
occurrence  of  nervous  worry,  and  that  after  the  cause 
of  the  nervous  worry  has  passed  away  tea  may  again 
be  taken,  in  moderation,  with  impunity.  In  irritable 
states  of  the  stomach,  tea  is  also  apt  to  disagree,  espe- 
cially if  the  coarser  teas  containing  much  tannin  are 
taken;  these,  when  taken  in  large  quantities  during, 
or  too  soon  after,  a  meal,  will  disturb  and  often  seriously 
hinder  the  digestive  processes." 

The  beneficial  effects  which  are  thought  to  belong 


IQ2     ALCOHOL,    TEA,    COFFEE,    TOBACCO,    OPIUM 

to  the  moderate  use  of  tea  and  coffee  are  no  doubt 
often  more  apparent  than  real;  they  produce  an 
agreeable  feeling,  which  makes  the  user  believe  that 
he  is  benefited  when  perhaps  only  a  harmful  change 
has  taken  place. 

If  no  other  harm  came  from  the  use  of  these  sub- 
stances than  the  constant  deception  as  to  the  true 
state  of  the  body,  even  that  would  be  considerable 
damage.  For,  if  the  proper  appetite  is  interfered 
with,  it  is  quite  certain  that  at  times  too  much  or 
too  little  food  will  be  taken.  Tea  and  coffee  have 
also  the  power  of  relieving  the  sense  of  fatigue,  and 
while  they  may  thus  be  valuable  aids  as  a  temporary 
relief  from  suffering,  they  become  very  harmful  if 
they  lead  us  to  overlook  and  disregard  the  cause  of 
the  weariness.  Fatigue  itself  has  its  uses,  and  we 
would  sooner  or  later  suffer  if  deprived  of  its  warn- 
ing voice.  In  other  words,  the  delicate  balance  of 
coordination  between  the  processes  of  nutrition  and 
necessities  of  the  various  organs  would  be  lost.  Such 
a  state  continued  could  not  result*  otherwise  than  inju- 
riously, the  extent  of  injury  depending  on  the  degree 
to  which  the  organism  was  affected.  The  claim  that 
tea  or  coffee  will  enable  the  body  to  do  more  work 
on  a  smaller  amount  of  food  is  absurd.  Energy  can 
not  come  from  nothing.  As  the  source  of  energy 
in  the  body  is  oxidation  of  oxidizable  substances 
(foods),  it  is  impossible  for  a  substance  to  cause  work 
to  be  done  by  doing  away  with  its  source  of  energy. 

Whatever  makes  us  "  feel  better  "  when  we  really 
are  not  better,  forces  our  nervous  system  to  tell  lies 
to  us.  This  "  feeling  better  "  is  followed  by  "  feel- 


TOBACCO  193 

ing  worse,"  which  is  also  a  lie.  These  waves  of 
feeling  caused  by  stimulants  destroy  the  unity  and 
effectiveness  of  life.  The  greater  the  wave  of  exalta- 
tion, the  lower  is  the  depression  which  follows.  This 
depression  finds  its  extreme  in  discouragement,  pes- 
simism, and  delirium  tremens.  The  user  of  stimulants 
leads  in  a  sense  a  double  life,  and  no  form  of  "  double 
life  "  can  be  an  effective  one. 

It  is  unwise  to  use  even  in  so-called  moderation 
these  stimuli  which  thus  distort  the  natural  action  of 
the  nervous  mechanisms  regulating  the  nutritive  pro- 
cesses. But  it  is  worse  than  folly  to  indulge  in  them 
to  an  excess  which  brings  on  one  the  most  serious 
results.  Between  moderation  and  excess  the  grada- 
tion is  very  gradual.  Moderation  in  the  great  major- 
ity of  cases  becomes  a  greater  or  less  degree  of  excess. 
It  is  certainly  the  part  of  wisdom  to  forego  the  passing 
pleasure  that  these  beverages  may  give,  and  avoid 
the  risk  of  the  more  lasting  suffering  or  disability 
which  their  use  may  entail. 

Tobacco. — Tobacco,  as  is  well  known,  consists  of 
the  leaves  of  a  plant  which  is  raised  in  many  warm 
countries.  It  is  used  in  the  form  of  snuff,  or  is  chewed, 
or  smoked  as  cigars,  cigarettes,  or  in  a  pipe.  It  was 
introduced  into  Europe  at  the  time  of  Queen  Eliza- 
beth by  Sir  Walter  Raleigh,  who  learned  its  qualities 
from  the  Indians  of  North  America.  From  this  time 
its  use  gradually  spread  throughout  the  civilized 
world. 

Among  the  many  substances  in  the  leaves  of  the 
tobacco  plant  the  most  characteristic  is  nicotine. 
This  is  oily  and  aromatic.  It  is  distilled  from  the 

IND,  PR.  PHYS. —  13 


194    ALCOHOL,    TEA,    COFFEE,    TOBACCO,    OPIUM 

leaves  by  the  heat  of  the  burning  tobacco.  The 
vapor  of  this  oil  is  partly  condensed  in  the  cigar  or 
cigarette,  or  in  the  bottom  of  the  bowl  or  along  the 
•stem  of  a  pipe;  but  part  of  it  passes  on  to  the  throat 
and  lungs  of  the  smoker. 

From  these  regions  it  gets  into  the  body.  Nicotine 
is  an  active  poison,  even  in  small  quantities.  The 
amount  that  usually  gets  into  the  body  by  the  user 
of  tobacco  is  very  small,  otherwise  the  results  would 
be  fatal.  As  it  is,  many  persons  use  tobacco  for 
many  years,  apparently  without  bad  effects.  The 
body,  which  at  first  is  greatly  shocked  at  the  intro- 
duction of  the  poison,  seems  later  to  adapt  itself  to 
its  presence.  Still  to  a  great  number  of  persons  it  is 
always  a  poison,  more  or  less  undermining  the  health, 
or  even  breaking  it  down  entirely ;  used  in  excess  — 
and  there  is  constantly  this  danger  —  the  results  are 
most  serious.  The  physiological  effects  of  tobacco 
are  as  follows: 

It  affects  the  heart,  and  excessive  use  may  produce 
palpitation  and  weakening  of  that  organ;  it  inter- 
feres with  the  digestion  and  causes  a  loss  of  appetite. 
A  long  series  of  carefully  conducted  experiments 
show  that  immediately  after  smoking  there  is  a 
marked  loss  of  the  power  of  doing  work  with  the 
voluntary  muscles.  Tobacco  is  also  said  to  interfere 
with  the  development  of  the  red  blood  coipuscles, 
whose  great  importance  has  been  shown  in  another 
place. 

Of  the  other  substances  besides  the  nicotine  which 
are  vaporized  by  the  heat  of  the  burning  tobacco, 
and  pass  with  the  smoke  into  the  mouth,  throat,  and 


OPIUM  195 

lungs,  some  produce  irritation  of  the  mucous  lining 
and  may  bring  about  a  diseased  state  of  those  organs, 
such  as  chronic  sore  throat  and  other  affections. 
It  is  thought  that  many  cases  of  cancer  of  the  mouth 
can  be  traced  to  the  habit  of  smoking.  It  is  agreed 
on  all  sides  that  the  use  of  tobacco  is  very  injurious 
to  the  young,  and  should  be  avoided  by  them  in  every 
form.  There  have  been  many  cases  recorded  of  death 
of  young  boys  through  nicotine  poisoning  from  excess 
in  smoking. 

The  evil  effects  of  tobacco  come  on  in  such  an  in- 
sidious way,  that  very  often  the  sufferer  has  no  hint 
of  the  true  cause  of  his  troubles;  this  renders  it  all 
the  more  a  dangerous  enemy. 

The  tobacco  habit  grows  on  a  person  till  it  becomes, 
in  the  great  majority  of  cases,  a  somewhat  tyrannical 
master,  demanding  great  sacrifices  of  time,  health, 
and  money  to  satisfy  its  desires.  This  itself  is  a  form 
of  disease.  There  is  another  point  of  view  we  should 
consider.  How  will  it  affect  our  associates?  Both 
smoking  and  chewing  are  offensive  to  most  people 
who  do  not  use  tobacco.  We  should  indeed  hesitate 
before  forming  a  habit  which  will  render  our  close 
presence  disagreeable  to  many,  if  not  to  most  of  our 
friends. 

Opium. — The  use  of  opium  or  some  of  its  com- 
pounds may  become  a  habit  impossible  to  control. 
When  this  is  the  case  the  result  is  usually  a  most 
disastrous  one.  Opium  occurs  in  various  forms. 
Morphine  is  a  substance  made  from  it.  Some  com- 
pound of  opium  is  found  in  many  medicines,  such 
as  paregoric  and  laudanum.  Many  of  the  so-called 


196    ALCOHOL,    TEA,    COFFEE,    TOBACCO,    OPIUM 

11  cough  mixtures  "  and  "  soothing  sirups  "  contain 
some  form  of  it.  It  is  a  very  dangerous  drug.  A 
small  amount  of  it  will  produce  death.  In  the  hands 
of  the  doctor  it  becomes,  in  disease,  one  of  the  most 
important  medicines;  but,  on  account  of  the  danger 
in  its  use,  it  should  be  given  only  under  direction  of 
a  physician.  The  frequent  use  of  medicines  contain- 
ing opium  or  its  compounds  may  lead  to  the  formation 
of  the  opium  habit. 

General  Considerations  in  Regard  to  Stimulants.  — 
The  body,  as  we  have  seen,  is  a  combination  of  deli- 
cately balanced  mechanisms.  Through  the  nervous 
system  many  of  them  are  self-regulating.  These 
work  most  correctly  when  the  stimuli  which  direct 
their  action  come  from  the  actual  condition  of  the 
body.  Thus  the  movements  of  respiration  are  con- 
trolled by  the  amount  of  carbonic  acid  in  the  blood. 
The  beat  of  the  heart  is  regulated  by  nervous  im- 
pulses arising  from  actual  conditions  of  various  parts 
of  the  body.  We  have  shown  that  the  actions  of  the 
glands,  and  of  other  organs,  are  regulated  in  a  similar 
manner.  Now,  if  any  artificial  stimulus  acts  on  these 
mechanisms,  they  no  longer  work  in  just  the  manner 
they  should,  to  be  in  harmony  with  the  remainder  of 
the  system.  The  body  is  then  not  in  its  best  con- 
dition. 

By  means  of  the  nervous  system  we  have  sensa- 
tions which  tell  us  of  the  outside  world  through  the 
special  senses,  and  of  the  state  of  our  own  body, 
as  in  hunger,  thirst,  fatigue,  pain,  etc.  Furthermore, 
we  have  the  power  of  coming  to  conclusions  in  regard 
to  our  actions  on  receiving  impressions  through  these 


CONSIDERATIONS  IN  REGARD   TO  STIMULANTS    197 

sensations.  The  whole  is  a  very  complex  means  by 
which  we  adapt  our  actions  to  conditions  in  which 
we  are  placed. 

For  the  greatest  success,  for  the  clearest  seeing, 
for  the  most  efficient  action,  it  is  of  the  utmost  im- 
portance that  correct  reports  come  in  for  the  judg- 
ment to  act  upon.  In  other  words,  we  wish  to  know 
the  world  as  it  really  is,  and  we  wish  to  know  the 
actual  conditions  of  the  body.  This  is  impossible 
when  the  sensations  are  modified  by  stimulants. 
They  make  us  fe'el  warm,  cool,  hungry,  thirsty,  well, 
or  ill,  when  we  are  not  really  in  such  condition.  We 
have  reporters  about  us  which  make  false  reports;  hence 
when  we  act  on  those  reports  our  conduct  can  not  be 
right. 

In  the  close  competition  we  are  sure  to  meet  with 
in  any  pursuit  in  life,  the  degree  of  success  will  depend 
upon  our  equipment.  How  great,  then,  is  the  im- 
portance of  keeping  in  good  condition  the  delicate 
mechanisms  upon  the  true  working  of  which  depend 
our  chances  of  success  and  our  capability  for  happi- 
ness! How  unwise  is  the  person  who  voluntarily 
does  anything  that  may  prove  a  hindrance  to  the  best 
action  of  his  mind  or  body! 


INDEX 


Abdomen,  87,  100. 
Absolute  alcohol,  181. 
Absorption,  from  small  intestine, 
92. 

from  stomach,  88,  89. 
Accommodation  of  eye,  157, 158. 
Adam's  apple,  103. 
Air,  impure,  106,  112,  113,  168. 

pressure  of,  98. 

pure,  105. 

Air  sacs  or  vesicles,  96. 
Air  tubes,  structure  of,  96. 
Albumen,  71. 
Alcohol,  as  medicine,  187,  188. 

description  of,  181. 

distillation  of,  183. 

effect    on    community,     189, 
190. 

effect  on  heart,  61,  62. 

effect  on  nervous  system,  145, 
146. 

physiological  action  of,   183- 
187. 

source  of,  181,  182. 
Alimentary  canal,  78,  79. 
Alkaline  contents  of  small  in- 
testine, 91. 
Antiseptics,  180. 
Aorta,  49,  50. 

arch  of,  50. 

Appetite,  use  and  abuse  of,  75, 
76. 


Aqueous  humor,  156. 

Arm  and  hand,  bones  of,  23-29. 

study  of,  12,  13. 
Arms,  function  of,  34,  35. 
Arteries,  aorta,  49,  50. 

blood  pressure  in,  53,  54. 

description  of,  46,  47. 

pulmonary  artery,  50. 

structure  of,  51. 
Arytenoid  cartilages,  103. 
Asphyxia,  114-116. 
Astigmatic  eyes,  163,  164. 
Auditory  apparatus,  159,  160. 
Auditory  nerve,  159,  160. 
Auricles,  49. 


Bacteria,  170-180. 
Bathing,  125,  126. 
Beans,  as  food,  72,  74. 
Biceps  muscle,  14,  26. 
Bicuspid  teeth,  81. 
Bile,  90,  91. 
Blood,  care  of,  58. 

coagulation  of,  57-60. 

composition  of,  56. 

corpuscles  of,  56,  57. 

course  of,  in  circulation,  52. 

flow  of,  in  arteries  and  veins, 

53,  54- 

in  hand,  45,  46. 
plasma,  57. 
pressure  of,  53,  54. 


199 


20O 


INDEX 


Blood  (continued}  — 

regulation  of  supply   of,    55, 
56. 

use  of,  44,  45. 

Blood  vessels,  structure  of,  51. 
Blubber  of  whale,  1 20. 
Body,  compared  to  an  engine, 
67,  68. 

composition  of,  69. 

divisions  of,  34. 

plan  of,  63,  64. 

proportion   of  foods  needed, 

74,  75- 

regulation  of  temperature  of, 
121,  122. 

wastes  of,  69. 

work  of,  66,  67. 

Bones,  as    levers,   29,    34,   37, 
38. 

hygiene  of,  41-43. 

of  arm  and  hand,  23-29. 

of  ear,  159. 

of  face,  36,  37. 

of  leg,  31-34- 

of  thorax,  36. 

structure  of,  39,  40. 

uses  of,  37. 
Bony  tissue,  65,  66. 
Brain,   bones  of  skull    protect, 
38. 

nerve  cells,  132,  133. 

part  of  nervous  system,  133, 

134- 

structure  of,  135,  136. 

weight  of,  135. 
Breastbone,  36. 
Breathing,  correct,  113,  114. 
Bronchi,  96. 
Bronchial  tubes,  96. 
Bruises,  169. 


Cabbage,  starch  in,  71. 
Caffeine,  191. 
Canine  teeth,  81. 
Canned  foods,  170,  171. 
Capillaries,  absorption  by,  55, 88, 
92. 

action  of,  55. 

description  of,  46,  47,  51. 
Carbon,  69. 
Carbon  dioxide,  in  air,  105,  106. 

in  circulation,  20. 

in  oxidation,  67,  69,  72,  73. 

in  respiration,  20,  95,  105,  106, 

124. 

Cardiac  opening  of  stomach,  87. 
Carpals,  24. 
Cartilage,  defined,  41. 

of  ribs,  36. 
Cement  of  tooth.  81. 
Central  nervous  system,  139. 
Cerebellum,  136. 
Cerebrum,  135,  140,  141. 
Cervical  vertebrae,  35. 
Cheese,  as  food,  72. 
Chest,  36. 
Chlorine,  69. 
Chlorophyll,  72. 
Cholera,  176. 
Choroid  coat  of  eye,  156. 
Cilia,  96,  97. 

Ciliary  muscle  of  eye,  156,  157. 
Circulatory  system,  blood, 44-48. 

blood  vessels,  46-50. 

divisions  of,  51. 

heart,  48. 

hygiene  of,  58-62. 

physiology  of,  52-58. 

regulation  of  actions  of,  55,  56. 
Clavicle,  27. 


INDEX 


201 


Cleanliness,  125,  126,  179. 
Clot,  57. 

Clothing,  127-129. 
Coagulation,  57,  58. 
Coats  of  eye,  155,  156. 
Coccyx  bone,  35. 
Cochlea,  160. 

Coffee,  effects  of,  62,  190-192. 
Collar  bone,  27. 
Commercial  alcohol,  181. 
Concave  glasses,  158. 
Conjunctiva  of  eye,  154,  162. 
Connective  tissue,  50,  65,  66. 
Consumption,  174,  175. 
Contractile  power   of    muscles, 

15,  17,  18. 

Convex  glasses,  158. 
Convolutions  of  cerebrum,  135. 
Cooking,  value  of,  94. 
Cords,  vocal,  103. 
Cornea  of  eye,  153,  157. 
Coronary  vein,  50. 
Corpuscles,  of  blood,  56,  57. 
Course  of  blood  in  circulation,  5  2 . 
Cranial  nerves,  137. 
Cranium,  36. 
Crawfish,  38. 
Cricoid  cartilage,  103. 
Cross-eye,  164. 

Crystalline  lens  of  eye,  156,  157. 
Currents,  air,  108,  109. 


Delirium  tremens,  146. 
Dentine  of  teeth,  81,  83. 
Dermis,  118,  119. 
Diaphragm,  97. 
Diffusion,  101. 

Digestive  system,  absorption,  92. 
alimentary  canal,  78,  79. 


Digestive  system  (continued}  — 

bile,  90,  91. 

care  of,  93,  94. 

esophagus,  86,  87. 

foods  requiring  digestion,  77, 
78. 

glands,  79. 

liver,  90. 

mastication,  81. 

mouth,  79-82. 

pancreas,  90. 

parts  of,  79. 

pharynx,  86,  87. 

processes  in  digestion,  78. 

saliva,  82. 

salivary  glands,  82. 

small  intestine,  89,  90. 

stomach,  87-89. 
Diphtheria,  173. 
Diseases,  causes  of,  168. 

infectious,  169-180. 

of  ear,  167. 

of  eye,  1 65 . 

power  of  body  against,  168, 

169. 

Dislocation  of  joint,  42,  43. 
Distilled  liquors,  183. 
Dorsal  vertebras,  35,  36,  97. 
Dyspepsia,  93. 


Ear,  care  of,  166,  167. 

parts  of,  159,  1 60. 
Enamel  of  tooth,  81,  83. 
Epidermis,  45,  117,  118. 
Epiglottis,  104. 
Erysipelas,  173,  174. 
Esophagus,  86,  87. 
Eustachian  tube,  159. 
Evaporation,  121,  122. 


202 


INDEX 


Excretions,  122,  124. 
Exercise,  21,  22. 

excessive,  22,  62. 

lack  of,  1 68. 
Expiration,  99,  100. 
External  auditory  canal,  159. 
External  ear,  159. 
Eye,  accommodation  to  different 
distances,  157,  158. 

care  of,  161-165. 

coats  of,  155,  156. 

external  parts  of,  153,  154. 

eyeball,  154. 

longsightedness,  158. 

seeing,  156,  157. 

shortsightedness,  158. 
Eyeball,  154. 
Eyelashes,  153. 
Eyelids,  153. 
Eye  strain,  163,  164. 


Face,  bones  of,  36,  37. 
Fats,  action  of  pancreatic  juice 
on,  90,  91. 

defined,  71. 

digestion  of,  78. 

in  skin,  119,  120. 
Fatty  tissue,  65. 
Femur  bone,  33. 
Fermentation,  182. 
Fibula  bone,  33. 
Fingers,  actions  of,  12,  13,  15. 

bones  of,  23,  24. 
Flavors,  151. 
Flies,  diseases  carried  by,  173, 

175,  176,  179. 
Floating  ribs,  36. 
Flour,  as  food,  74. 
Food  groups,  70.    • 


Foods,  canned,  170,  171. 
fats,  71. 
forms  of,  70. 
inorganic,  70,  73. 
need  for,  63,  67-69. 
organic,  70,  71. 
oxidation  of,  72. 
properties    needed    in  body, 

74,  75- 

proteids,  71. 

use  and  abuse  of,  75,  76. 

See  also  Digestive  system. 
Forearm,  bones  of,  24-26. 
Forelimbs    of    lower    animals. 
29,  30. 

G 

Ganglia,  136,  137. 
Gastric  juice,  88. 
General  sensations,  147,  148. 
Germs,  disease,  169-172. 
Gills  offish,  97,98. 
Glands,  79,  120-122.  124. 
Graham  flour,  as  food,  74. 
G/ains,  as  food,  72. 
Gray  matter,  134. 
Growth  and  repair,  68. 
Gums.  70,  78. 

H 

Habits,  144,  145. 
Hair,  118,  123,  126. 
Hand  and  arm,  blood  in,  45,  46. 

bones  of,  23-29. 

movements  of,  12,  13. 
Hearing,  148,  158-160. 
Heart,  action  of,  52,  53. 

bones  of  chest  protect,  38. 

care  of,  60. 

description  of,  48. 

effect  of  alcohol  on,  61,  62. 

function  and  position  of,  48. 


INDEX 


203 


Heart  (continued}  — 

interior  of,  49. 

structure  of,  50,  51. 

valves  of,  49. 
Heat,  production  of,  67,  68. 

source  of,  121. 
Hemispheres  of  brain,  135. 
Hepatic  vein,  92. 
Hip  bone,  33. 
Hip  joint,  33,  40. 
Humerus,  26. 
Hunger,  149. 
Hydrogen,  69. 
Hygiene,  of  bones    and  joints, 

41-43- 

of  circulation,  58-62. 
of  digestive  organs,  93,  94. 
of  ear,  166,  167. 
of  eye,  161-165. 
of  muscles,  20-22. 
of  nervous  system,  142-146. 
of  respiration,  105-115 
of  skin,  125-129. 
of  teeth,  83-85. 


Incisor  teeth,  81. 
Incus  bone,  159. 
Indigestion,  93. 
Infectious  diseases,  169-180. 
Inferior  vena  cava,  50,  92. 
Inorganic  foods,  70*,  73. 
Insanity,  146. 
Inspiration,  99,  100. 
Instep,  31. 

Intercostal  ribs,  100. 
Internal  ear,  159,  160. 
Intestinal  juice,  90. 
Intestine,  large,  91,  92. 
small,  89,  90. 


Intoxication,  188,  189. 
Involuntary  actions,  141,  142. 
Involuntary  muscles,  19. 
Iris,  154,  156,  157. 
Iron,  69. 

Jawbone,  36,  37. 

Jellyfish,  39. 

Joints,  dislocation  of,  42,  43 

hygiene  of,  41-43. 

structure  of,  39,  40. 

K 

Kidneys,  124. 
Kneecap,  33,  34. 
Knee  joint,  33. 
Knuckles,  23. 

L 

Lachrymal  ducts,  153. 
Lacteals,  90. 
Larynx,  96,  103. 
Leg,  bones  of,  31-34. 

function  of,  34,  35. 
Lettuce,  starch  in,  71. 
Levers  of  body,  29. 
Ligaments,  defined,  40. 

injury  to,  42,  43. 
Lime,  69. 
Liver,  90,  92. 
Longitudinal  fissure,  135. 
Longsightedness,  158. 
Lower  maxillary  bone,  36.  37 
Lumbar  vertebrae,  35. 
Lungs,  description  of,  96-99. 

effect  of  tobacco  on,  1 14, 
Lymphatics,  88. 

M 

Malaria,  176,  177. 
Malleus  bone,  159. 
Marrow  of  bone,  40. 


204 


INDEX 


Mastication,  82. 

Maxillary  bones,  36,  37. 

Measles,  173,  174. 

Meat,  72,  74. 

Medulla  oblongata,  135,  136. 

Membrana  tympani,  159,  160. 

Membrane,  41. 

Mesentery,  89. 

Metacarpals,  23,  24. 

Metatarsals,  31,  33. 

Middle  ear,  159. 

Mildews,  72. 

Milk,  71,  72. 

Mitral  valve,  49. 

Molar  teeth,  81. 

Molds,  72. 

Mosquitoes,  carriers  of  disease 

germs,  177-179. 
Motions,  number  of,  16,  17. 

production  of,  16,  17. 
Mouth,  79,  80,  96. 
Mucous  coat  of  small  intestine, 

89,  90. 

Mucous  coat  of  stomach,  88. 
Mucous  membrane  of  air  tubes, 

96. 

Mucus,  80,  96,  97. 
Muscle  fiber,  133. 
Muscles,  care  of,  20-22. 

contractile  power  of,  15, 17, 1 8. 

description  of,  13-15. 

in  lower  animals,  17. 

involuntary,  19. 

number  of,  16. 

voluntary,  19. 
Muscular  tissue,  50,  65,  66. 
Mushrooms,  72. 


N 


Nails,  123,  127. 


Narcotics,  60-62. 
Nearsightedness,  163,  164. 
Nerve  cells,  132,  133. 
Nerve  center,  148. 
Nerve  fiber,  132,  134. 
Nerves,  cranial,  137. 

description  of,  18,  132. 

in  arm,  18,  130,  131. 

part   of  nervous  system,  133, 

134- 

sensory,  148. 

spinal,  137. 
Nervous  control  of  respiration, 

100. 
Nervous  impulses,  18,   19,   131, 

139,  140. 
Nervous  system,  action  of,  139. 

brain,  135-137. 

care  of,  142-144. 

effects    of   alcohol    on,    145, 
146. 

habits,  144,  145. 

involuntary  actions,  14.1,  142. 

nerve  cells,  134. 

nerve  fibers,  132,  133. 

nerves,  132. 

nervous  impulses,  18,  19,  131, 
139,  140. 

parts  of,  133,  134. 

spinal  cord,  134,  135,  137. 

sympathetic  system,  137. 

voluntary'actions,  140,  141, 
Nervous  tissue,  65.  66. 
Nicotine,  114,  193-195. 
Nitrogen  in  air,  105. 

in  proteids,  72,  73. 

in  tissues,  69. 
Nitrogenous  foods,  72,  74. 
Non-nitrogenous  foods,  72,  74. 
Nostrils,  96. 


INDEX 


205 


Occipital  bone,  134. 
•Odors,  152. 
Oil  glands,  118. 
Oils,  71,  78. 
Opium,  195,  196. 
Optic  nerve,  155,  156, 
Organ,  denned,  63. 
Organic  foods,  70,  71. 
Organisms,  65. 
Organization  in  body,  64,  65. 
Os  innominatum,  33. 
Osseous  tissue,  69. 
Oxidation,  67-69,  72,  73. 
Oxygen,  in  air,  105,  106. 

in  circulation,  20,  57. 

in  oxidation,  67-69. 

in    respiration,   95,    97,    101, 
102. 

P 

Pain,  148,  149. 
Palate,  80. 
soft,  151. 
Pancreas,  90. 
Pancreatic  juice,  90. 
Papillae  of  skin,  119. 
Patella  bone,  33,  34. 
Peas,  as  food,  72,  74. 
Pelvic  arch,  35. 
Peptones,  88,  90. 
Pericardial  liquid,  50. 
Pericardium,  50. 
Perspiration,  79,  120-122. 
Phalanges,  23,  31. 
Pharynx,  86,  87,  96. 
Phosphorus,  69. 
Pinna,  159. 
Plasma,  56,  57. 
Poisons,  184. 
Portal  vein,  92. 


Potassium,  69. 

Potatoes,  food  substances  in,  71, 

72,  74- 

Premolar  teeth,  81. 
Pressure  of  blood,  53,  54. 
Processes,  35.  . 

Proteids,  action  of  gastric  juice 
on,  88. 

action  of  pancreatic  juice  on, 
90. 

digestion  of,  78. 

foods  containing,  71,  72, 

oxidation  of,  73. 
Pulmonary  artery  and  veins,  49, 

50. 

Pulmonary  circulation.,  51. 
Pulp  of  tooth,  81. 
Pulse,  46,  53,  54. 
Pupil  of  eye,  154. 
Pylorus,  87. 

R 

Radius  bone,  25,  26. 
Reflex  actions,  141,  142. 
Repair  and  growth,  68. 
Respiration,      amount    of     air 
breathed,  101. 

artificial,  114-116. 

in  lower  animals,  97,  98. 

nervous  control^  100. 

respiratory  acts,  99,  100. 

respiratory  organs,  96,  97, 
Retina,  156. 
Ribs,  36-38,  97. 
Rice,  74. 
Rods  and  cones  of  eye,  156,  I57« 


Sacrum  bone,  35. 
Salines,  73. 
Saliva,  82. 


206 


INDEX 


Salivary  glands,  80,  82. 
Scapula  bone,  26,  27. 
Scarlet  fever,  173,  174. 
Sclerotic  coat  of  eye,  155. 
Secretion  of  glands,  79, 120-122, 

124. 

Seeing,  156,  157. 
Semicircular  canals,  160.        ^ 
Semilunar  valves,  49. 
Sensations,  defined,  147. 

general  and  special,  147,  148. 
Sense  organs,  133,  148. 
Sensory  nerves,  148. 
Shortsightedness,  158. 
Shoulder  blade,  26. 
Shoulder  girdle,  23. 
Shoulder  joint,  40. 
Sight,  148,  153-158- 
Skeleton,  animals  without,  39. 

bones  of  arm  and  hand,  23-30. 

bones  of  face,  36,  37. 

bones  of  leg,  31-34. 

bones  of  thorax,  36. 

different  kinds  of,  38. 

divisions  of  body,  34,  35. 

skull,  36. 

spinal  column,  35. 
Skin,  as  organ  of  temperature, 

122,  123. 

care  of,  125-129. 

structure  of,  117,  118. 

sweat  glands  in,  120,  122. 

touch  organs  in,  122,  150,  151. 

uses  of,  123,  124. 
Skull,  36. 
Sleep,  function  of,  143. 

lack  of,  1 68. 
Smallpox,  173,  174. 
Smell,  148,  152. 
Sodium,  69. 


Sore  eyes,  165. 

Sound,  sensation  of,  158,  160. 

Special  sensation,  148. 

Special-sense  organ,  148. 

Spinal  canal,  36. 

Spinal  column,  35,  37. 

Spinal  cord,  nerve  cells  in,  132, 

133- 
part  of  nervous  system,  132- 

134- 

position  of,  36. 

structure  of,  134,  135. 
Spinal  nerves,  137. 
Sprain,  42,  43,  169. 
Stapes  bone,  159,  160. 
Starches,    action   of  pancreatic 
juice  on,  90. 

digestion  of,  78,  82. 

foods  containing,  70-72. 
Sternum,  36,  97. 
Stimulants,  181-197. 
Stimulation  of  muscles,  19. 
Stimulus,  nervous,  19,  130. 
Stomach,  87-89. 
Subclavian  vein,  left,  92. 
Sugar,  digestion  of,  77,  78. 

foods  containing,  70-72. 
Sulphur,  69. 

Superior  vena  cava,  50,  92. 
Swallowing,  87. 
Sweat,  79,  120-122. 
Sweat  glands,  79,  120,  122. 
Sweet  potatoes,  starch  in,  71. 
Sympathetic     nervous    system, 

137- 

Systemic  circulation,  51. 
Systems,  64. 

T 

Tannin,  190,  191. 
Tarsals,  31,  33. 


INDEX 


207 


Taste,  organs  of,  80,  148. 

sense  of,  151,  152. 
Tea,  62,  190-192. 
Tear  ducts,  153. 
Tears,  79,  153. 
Teeth,  care  of,  83-85. 

description  of,  80,  81 . 

structure  of,  81. 

Temperature,     of     body,     121, 
122. 

sense  of,  148.  150,  151. 
Tendons,  13-15,  40. 
Theine,  190,  191. 
Thirst,  149. 
Thorax,  bones  of,  36. 

in  respiration,  96,  97. 
Thumb,  23,  24. 
Thyroid  cartilage,  103. 
Tibia  bone,  33. 
Tissues,  65,  66. 
Tobacco,   physiological    effects 

of,  62,  114,  193-195. 
Tongue,  80,  151. 
Tooth,  see  Teeth. 
Touch,  122,  148-151. 
Trachea,  96. 
Tricuspid  valve,  49. 
Tuberculosis     of    lungs,     174, 

*75- 

Typhoid  fever,  175,  176. 

U 

Ulna  bone,  24-26. 
Urea,  69,  124. 


Vaccination,  174. 
Valves  of  heart,  49,  5  it- 


Veins,  described,  47. 

flow  of  blood  in,  54. 

function  of,  50. 

structure  of,  51. 
Ventilation,  106-112. 
Ventricles,  49. 
Vertebrae,  35,  36,  97. 
Vertebrates,  38. 
Vestibule  of  ear,  160. 
Vibrations,  158,  159. 
Villi  of  small  intestine,  90. 
Vision,  distinct,  157. 
Vitreous  humor,  156. 
Vocal  cords,  103. 
Voice,  103. 

Voluntary  actions,  140,  141. 
Voluntary  muscles,  19. 

W 

Wall-eye,  164. 
Wastes  of  body,  69,  124. 
Water,  as    inorganic    food,   73, 

74- 

excretion  of,  122,  124. 

germs  carried  by,  176. 

in  air,  105. 

in  digestion,  78. 

in  oxidation,  67,  72. 

in  tissues,  69. 
White  matter,  134. 
Will,    muscles    controlled     by, 

18,  19. 

Wounds,  59,  169,  179,  180. 
Wrist,  24. 


Yeast,  181-183. 
Yellow  fever,  177,  178. 


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